Adaptive thrust vector unmanned aerial vehicle

ABSTRACT

A method for unmanned delivery of an item to a desired delivery location includes receiving, at an unmanned vehicle, first data representative of an approximate geographic location of the desired delivery location, receiving, at the unmanned vehicle, second data representative of a fiducial expected to be detectable at the desired delivery location, using the first data to operate the unmanned vehicle to travel to the approximate geographic location of the desired delivery location, upon arriving at the approximate geographic location of the desired delivery location, using the second data to operate the unmanned vehicle to detect the fiducial; and upon detecting the fiducial, using the fiducial to operate the unmanned vehicle to deliver the item.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/870,727, filed Jan. 12, 2018 which is a continuation-in-part U.S.application Ser. No. 14/581,027 filed on Dec. 23, 2014 which claimspriority to U.S. Provisional Application Ser. No. 61/920,913, filed Dec.26, 2013, and is also a continuation-in-part of U.S. application Ser.No. 15/316,011 filed on Dec. 2, 2016 which claims priority toInternational Application Number PCT/US2015/033992, filed Jun. 3, 2014,and U.S. Provisional Application No. 62/007,160 filed Jun. 3, 2014, andfurther claiming priority to U.S. Provisional Application No. 62/445,720filed Jan. 12, 2017, and U.S. Provisional Application No. 62/446,785filed Jan. 16, 2017, the entire contents of these applications beingincorporated herein by reference.

BACKGROUND

This invention relates to unmanned delivery of items to specifiedlocations using unmanned aerial vehicles (UAVs).

Traditionally, delivery companies such as UPS and FedEx deliver items tocustomers using delivery vehicles (e.g., trucks) which are operated bydelivery people. The delivery vehicles travel a predetermined route anddeliver packages to customer locations along the route. At the customerlocation, the delivery person verifies that the delivery location (e.g.,customer address) is correct and then leaves the package in a safe placeat the delivery location.

In recent years the use of UAVs has become widespread, particularly inmilitary and recreational applications. Until recently, commercial useof UAVs was limited due to the technological constraints of UAVs (e.g.,limited range, poor reliability, etc.) as well as the relatively highcost of UAVs.

Due to advances in technology and an increased prevalence of UAVs, UAVsare becoming cost effective and sufficiently reliable for use incommercial applications.

At the same time, there is a need for a cost effective, efficient meansof delivering items to customers over the last miles between a deliveryhub/fulfillment center and the customer's location.

Many groups have proposed using drones for delivery. Recently, Amazonhas presented the idea of delivering packages to customer locations overthe last mile using autonomous multi-rotor vehicles. It is unclear howthe vehicles employed by these groups accurately maneuvers the drones todeliver items, verify that the delivery location is correct, or decidewhere to safely leave packages.

SUMMARY

Preferred embodiments of unmanned aerial vehicles described hereinrelate to systems and methods for navigating aerial vehicles totransport objects. Such battery powered UAVs can include multi-rotorsystems that can both hover and fly with one or more rotors oriented topropel the vehicle in one direction. Aerodynamic flights surfaces canprovide lift and steering functions. In certain embodiments, the UAVcomprises a plurality of hover rotors, and one or more propelling rotorsthat can be vertically oriented or tilted to drive the UAV in a selecteddirection. The UAV can be steered using the hovering rotors which can beselectively driven and/or oriented or can be used with flight controlsurfaces on the spars or wings of the UAV to adjust the direction offlight. A navigation device on the UAV can be used to control flightoperations as described herein. One or more processors on the UAV can beprogrammed to automate the delivery of objects

In an aspect, in general, a method for unmanned delivery of an item to adesired delivery location includes receiving, at an unmanned vehicle,first data representative of an approximate geographic location of thedesired delivery location, receiving, at the unmanned vehicle, seconddata representative of a fiducial expected to be detectable at thedesired delivery location, using the first data to operate the unmannedvehicle to travel to the approximate geographic location of the desireddelivery location, upon arriving at the approximate geographic locationof the desired delivery location, using the second data to operate theunmanned vehicle to detect the fiducial, and upon detecting thefiducial, operating the unmanned vehicle to travel to the deliverylocation and deliver the item.

Aspects may include one or more of the following features.

The fiducial may be selected from a group including a two-dimensionalcode, a QR code, or a bar code. Using the second data to operate theunmanned vehicle to detect the fiducial may include capturing imagesusing a camera mounted on the unmanned vehicle and processing thecaptured images to determine if the fiducial is represented in theimages. Operating the unmanned vehicle to deliver the item may includeoperating a winch mounted on the unmanned vehicle to lower the item tothe ground. Prior to operating the winch to lower the item to theground, the unmanned vehicle may determine whether any obstructions arepresent in the delivery location.

Delivery of the item to the delivery location may be aborted if theunmanned vehicle determines that obstructions arc present in thedelivery location. Operating the unmanned vehicle to deliver the itemmay include causing the vehicle to drop the item into a receptacle. Thereceptacle may be configured to soften the landing of the item.Operating the unmanned vehicle to deliver the item may include landingat the delivery location and then dropping the item at the deliverylocation. The method may also include notifying a customer that the itemhas been delivered to the delivery location after delivering the item tothe delivery location. Notifying the customer may include one or more ofsending an email to the customer or sending a text message to thecustomer.

The first data representative of an approximate geographic location ofthe desired delivery location may be determined from a mapping of streetaddresses to global positioning system coordinates. Using the first datato operate the unmanned vehicle to travel to the approximate geographiclocation of the desired delivery location may include notifying acustomer of an estimated time of arrival of the item at the deliverylocation. Notifying the customer may include one or more of sending anemail to the customer or sending a text message to the customer. Thefiducial may include a radio-frequency beacon. The radio-frequencybeacon may include a near-field communication radio frequency signal.

Receiving the first data representative of an approximate geographiclocation of the desired delivery location may include receiving thefirst data from a mobile device and using the second data to operate theunmanned vehicle to detect the fiducial may include detecting thefiducial as generated from the mobile device. The method may alsoinclude updating the first data representative of an approximategeographic location of the desired delivery location as the mobiledevice moves. The fiducial may be a permanently installed fiducialassociated with the delivery location. The fiducial may be auser-printed fiducial.

In another aspect, in general, a method for unmanned delivery of an itemto a desired delivery location includes receiving, at an unmannedvehicle, first data representative of an approximate geographic locationof the desired delivery location, receiving, at an unmanned vehicle,second data including a mapping of wireless network identifiers torepresentations of geographic locations, using the first data to operatethe unmanned vehicle to travel to the approximate geographic location ofthe desired delivery location, and upon arriving at the approximategeographic location of the desired delivery location, using the seconddata to operate the unmanned vehicle to travel to the delivery locationand deliver the item.

Using the second data to operate the unmanned vehicle to travel to thedelivery location may include determining the delivery location usingtriangulation of a plurality of wireless networking signals in an areaof the delivery location.

In another aspect, in general an unmanned aerial vehicle for delivery ofa package includes a fuselage including a package bay and a liftingsurface, a plurality of rotors affixed to the fuselage, wherein theunmanned aerial vehicle is operable in a first mode with the rotorsoperating in a substantially horizontal configuration, and the unmannedaerial vehicle is operable in a second mode with at least some of therotors operating in a substantially vertical configuration.

In the exemplary embodiment, the unmanned vehicle is a multi-rotorvehicles (e.g. quadcopters, hexacopters, octocopters). The multi-rotorvehicles generally have motors rigidly mounted to the airframe andcontrol vehicle motion by adjusting thrust of individual motors based onan idealized model of all motors generating thrust in the verticaldirection. This makes for a system which can only be controlled in roll,pitch, yaw, and net thrust. Such a multi-rotor vehicle can move in spaceby holding a particular roll or pitch angle and varying the net thrust.This approach can lead to system instability as the vehicle hovers.Hover quality can be improved by controlling each axis independently ofthe vehicle's roll and pitch.

Approaches described herein use a hybrid multicopter configuration thatuses a propeller in the vertical plane for propulsion and a liftingsurface to supplement the rotors in forward flight. Configurationsinclude a simple multicopter, a multicopter with a pusher prop, and amulticopter with pusher prop and a lifting surface. Each configurationincludes a performance analysis.

Approaches described herein employ thrusters which arc mounted to amulti-rotor helicopter frame of the unmanned aerial vehicle withdihedral and twist. That is, the thrust directions are fixed, and notall parallel. Each thruster generates an individual thrust line which isgenerally not aligned with the thrust lines of other thrusters.Free-body analysis yields the forces and moments acting on the body fromeach thruster. The forces and moments are summed together to produce aunique mapping from motor thrust to net body forces and moments. Adesired input including roll, pitch, and yaw moments and forward,lateral, and vertical thrusts can be received and used to calculate thenecessary change in motor thrusts, and thus by extension motor speeds,to achieve the desired input.

Approaches described herein use statically mounted thrusters to developnet thrusts (e.g., a net horizontal or vertical thrust) without changingthe net roll, pitch, and yaw torques.

Approaches described herein use statically mounted thrusters to developnet moments without changing net thrusts generated by the motors. Afurther embodiment provides for the mounted thrusters to changedirection to provide a plurality of flight modes. A fine adjustment ofthruster direction can be included for a plurality of thrusters or allthe thrusters. A plurality of services can be used to provide finedirection adjustment within a plane of within a cone. A plurality of thethrusters can each include a second motor to rotate the associatedthruster between two or more flight modes as described in greater detailherein.

In an aspect, in general, an aerial vehicle includes a body having acenter and a number of spatially separated thrusters. The spatiallyseparated thrusters are statically coupled to the body at locationsaround the center of the body and are configured to emit thrust along anumber of thrust vectors. The thrust vectors have a number of differentdirections with each thruster configured to emit thrust along adifferent one of the thrust vectors. One or more of the thrust vectorshave a component in a direction toward the center of the body or awayfrom the center of the body.

The thrust vectors may be emitted in six different directions. Thethrust vectors may be emitted in eight different directions. The thrustvectors may be emitted in ten different directions. The thrusters may bedistributed symmetrically about the center of the body. The thrustersmay be distributed on a plane defined by the body.

All of the thrust vectors may have a shared primary component in a firstdirection. The first direction is may be a vertical direction. Theaerial vehicle may include a controller configured to receive a controlsignal characterizing a desired spatial position for the aerial vehicleand a desired spatial orientation for the aerial vehicle, determine anet force vector and a net moment vector based on the received controlsignal, and cause the thrust generators to generate the net force vectorand the net moment vector. The controller may be further configured tocause the thrust generators to vary the net force vector whilemaintaining the net moment vector. The controller may be furtherconfigured to cause the thrust generators to vary the net moment vectorwhile maintaining the net force vector. The body may include a number ofspars and each thruster of the number of thrusters is statically coupledto an end of a different one of the spars.

Each thruster may include a motor coupled to a propeller or turbine. Themotors of a first subset of the number of thrusters may rotate in afirst direction and the motors of a second subset of the number ofthrusters may rotate in a second direction, different from the firstdirection. The motors for all of the thrusters may rotate in a samedirection. The motors of a first subset of the number of thrusters mayhave a first maximum rotational velocity and the motors of a secondsubset of the number of thrusters may have a second maximum rotationalvelocity, less than the first maximum rotational velocity. At least someof the thrusters may be coupled to the body at a dihedral angle relativeto the body and/or at least some thrusters may be coupled to the body ata twist angle relative to the body.

The aerial vehicle may include an imaging sensor coupled to the body.The aerial vehicle may include an aerodynamic body covering disposed onthe body. The imaging sensor may be statically coupled to the body. Theimaging sensor may be coupled to the body using a gimbal. The imagingsensor may include a still camera. The imaging sensor may include avideo camera.

In some aspects, the aerial vehicle is configured to maintain a desiredspatial orientation while at the same time generating a net thrust thatvaries in magnitude and/or direction). In some aspects, a sensor such asa still or video camera is statically coupled to the multi-rotor vehicleand an orientation of the vehicle is maintained such that the cameraremains pointed in a given direction while the net thrust vectorgenerated by the vehicle causes the vehicle to move in space. Note thatthe sensor can comprise the camera, the IMU, the GPS sensor, thepressure sensor, or other sensors that control flight operation. Thecontrol system can include a processor that computes updated motorspeeds and twist angles.

Preferred embodiments employ a control system that communicates with anexternal flight management system to control flight operations of theunmanned aerial vehicle. The control system on the unmanned aerialvehicle can comprise a system-on-chip (SOC) that includes one or moreintegrated circuits having one or more memories to process sensor dataand stored instructions regarding flight path, payload operation andnumerous flight control operations as described herein. The one or moreintegrated circuits can include field programmable gate arrays (FPGA)and/or application specific integrated circuits (ASIC).

Among other advantages, certain aspects employ a first navigationtechnology to travel to an approximate area of a delivery location andthen use a second navigation technology to very accurately travel to theexact delivery location. Approaches allow for a decoupling of thepositional control of the multi-rotor helicopter from the rotationalcontrol of the multi-rotor helicopter. That is, the position of themulti-rotor helicopter can be controlled independently of the rotationof the multi-rotor helicopter. The system can include a plurality ofrotor tilt positions including a parallel axis mode, a multi-axis mode,and a flight mode in which a plurality of rotors are tiled for forwardflights.

Dynamic in-air stability is improved using the multi-axis mode in whichthe thrust vectors of each motor are oriented on different axes. Thenumber of parts necessary to orient a camera at a given angle isreduced. This leads to cheaper, more robust models that perform betterin a wide variety of conditions.

By using motors that all rotate in the same direction, the number ofunique parts required to build the aerial vehicle is reduced, resultingin a reduced cost for the aerial vehicle.

By using motors that may rotate in different directions, stability,desired spatial positioning, and desired spatial orientation for themulti-rotor helicopter is improved, resulting in an improved ability todeliver items.

Other features and advantages of the invention are apparent from thefollowing description, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is an unmanned Vehicle delivery system.

FIG. 2 is an unmanned vehicle detecting a fiducial.

FIG. 3 is an unmanned vehicle delivering a package onto a fiducial.

FIG. 4 is an unmanned vehicle detecting a fiducial on a customer'smobile device.

FIG. 5 is an unmanned vehicle delivering a package to a customer.

FIG. 6 is an unmanned vehicle performing visual location matching.

FIG. 7 is an unmanned vehicle navigating using WiFi signals.

FIG. 8 is an unmanned vehicle delivering a package to a delivery siteusing WiFi signals.

FIG. 9 is an unmanned vehicle courier system.

FIG. 10 is an unmanned vehicle courier system delivering an item.

FIG. 11 is a package receptacle including a decelerating slide.

FIG. 12 is a package receptacle including a net.

FIG. 13 is a flowchart of a first exemplary UAV delivery to a location.

FIG. 14 is a flowchart of a second exemplary UAV delivery to a location.

FIG. 15 is a flowchart of a third exemplary UAV delivery to a location.

FIG. 16 is a flowchart of a fourth exemplary UAV delivery to a location.

FIG. 17 is a flowchart of a fifth exemplary UAV delivery to a location.

FIGS. 18A-18J describe hybrid multicopter configurations and performanceanalysis of the hybrid multicopter configurations.

FIG. 19 is an unmanned aerial vehicle in a multi-copter mode.

FIG. 20 is an unmanned aerial vehicle in a first forward flight mode.

FIG. 21 is an unmanned aerial vehicle in a second forward flight mode.

FIG. 22 is a side view of the unmanned aerial vehicle.

FIG. 23 is a side view of an unmanned aerial vehicle with a rotatablespar and rotor.

FIG. 24 is a perspective view of a multi-rotor helicopter.

FIG. 25 is a side view of a multi-rotor helicopter.

FIG. 26 is a detailed view of a thruster of the multi-rotor helicopter.

FIG. 27 is a block diagram of a first control system.

FIG. 28 is a block diagram of a second control system.

FIG. 29 shows the multi-rotor helicopter operating in the presence of aprevailing wind.

FIG. 30 shows the multi-rotor helicopter rotating without changing itsposition.

FIG. 31 shows the multi-rotor helicopter including a gimbaled imagingsensor hovering.

FIG. 32 is a plot showing a roll and pitch controllability envelope inNm at various weights, with no lateral thrust being generated.

FIG. 33 is a plot showing a roll and pitch controllability envelope inNm at various weights with a 1 m/s² rightward thrust being generated.

FIG. 34 is a plot showing a roll and pitch controllability envelope inNm at various weights with a 1 m/s² forward thrust being generated.

FIG. 35 is a plot showing a roll and pitch controllability envelope inNm at various weights with a 1 m/s² forward thrust and 1 m/s² tightthrust being generated.

FIG. 36 is a flowchart of an exemplary operation of a multi-rotor UAVconverting between a multi-copter mode and a forward flight mode.

FIG. 37 is a flowchart of an exemplary multi-rotor UAV flying a longdistance in forward flight mode and a short distance in multi-coptermode.

FIG. 38 illustrates a flight control system for a six rotor unmannedaerial vehicle.

FIG. 39 illustrates a system for flight control of UAV corridors toprovide traffic management and collision avoidances.

FIG. 40 illustrates an 8 rotor system having a plurality of flight modeswith a sensor array for collision avoidance.

FIG. 41 illustrates the system of FIG. 39 with rotors tilted ontoparallel axes for high speed flight.

FIG. 42 illustrates a six rotor system for adaptive thrust control ofUAV flight operations.

FIG. 43 illustrates a system for tilting a rotor thrust axis to alterthe thrust vector.

FIG. 44 is a flowchart of an exemplary multi-rotor UAV configured totilt one or more rotors while traveling a route.

FIG. 45 is a block diagram of a third control system.

FIG. 46 is an schematic block diagram of at least one sensor used in amulti-rotor helicopter control system for controlling a vehicle.

FIG. 47 is a flowchart of an exemplary multi-rotor UAV configured todeliver items to a mobile delivery location.

DESCRIPTION

Referring to FIG. 1 , an unmanned vehicle delivery system 100 receivesan order for an item 102 from a user 104 via, for example, a computer105. Using information included in the order, the system 100 deliversthe item 102 to a delivery location 106 specified by the user 104 usingan unmanned delivery vehicle 108 (e.g., an unmanned aerial vehicle).

When the user 104 places the order, the order is transmitted over anetwork 110 (e.g., the internee) to a retailer (e.g., an onlineretailer) 112 where the order is initially processed. After initiallyprocessing the order, the retailer 112 sends order information to aregional distribution center 114 which is located in the samegeographical region as the delivery location 106. At the regionaldistribution center 114, the item 102 is attached to the unmanneddelivery vehicle 108. The unmanned delivery vehicle 108 is alsoprogrammed with instructions (e.g., GPS coordinates associated with thedelivery location 106) for delivering the item to the delivery location106.

Once the unmanned delivery vehicle 108 has the item 102 attached theretoand is programmed with instructions for delivering the item 102 to thedelivery location 106, the unmanned delivery vehicle 108 launches anddelivers the item 102 to the delivery location 106.

After delivering the item 102, the unmanned delivery vehicle 108 returnsto the regional distribution center 114 where it retrieves another item,is reprogrammed, and repeats the delivery process.

While the general unmanned delivery process described above seemssimple, a number of challenges to the process exist. The examplesdescribed in detail below address the challenges to the unmanneddelivery process and improve the overall performance of the process.

Referring to FIGS. 1 and 2 when a customer orders an item as describedin FIG. 1 , the customer provides a shipping address (i.e., the addresswhere they want their item delivered). The retailer then provides thecustomer with a printable fiducial 216. In some examples, the printablefiducial 216 is in the form of a QR code or a bar code which is specificto the customer (and possibly unique to the order). The online retailerthen instructs the customer to print the fiducial 216 and to place itoutdoors in a location where they want their item to be delivered (i.e.,the delivery location 106). In some examples, the online retailer alsoinstructs the customer to place the fiducial 216 in a location that iseasily accessible by a UAV 108 (e.g., a location unobstructed by trees,fences, power lines, and so on). The customer prints the fiducial 216,places the printed fiducial 216 in a location outside of their house218, and waits.

At the same time at the regional distribution center 114 near thecustomer's house 218, a package including the customer's item 102 isloaded onto an unmanned aerial vehicle (UAV) 108 (e.g., a multi-rotorUAV) and the UAV 108 is programmed to fly to a Global Positioning System(GPS) coordinate associated with the customer's address. In someexamples, the GPS coordinate is obtained from a mapping service such asGoogle Maps which approximately maps GPS coordinates to streetaddresses.

Once programmed, the UAV 108 leaves the regional distribution center 114and flies toward the GPS coordinate associated with the customer'saddress. When the UAV 108 reaches the GPS coordinate, the UAV 108 beginsto fly around the GPS coordinate in an efficient manner. At the sametime, a camera 220 on board the UAV 108 is activated and begins takingstill photographs or video of the surrounding area. An image processorprocesses the photographs or video to determine whether the fiducial 216is present in the photographs or video.

Referring to FIG. 3 , once the fiducial 216 is detected, the UAV 108flies toward the fiducial 216 until the UAV 108 is directly above thefiducial 216. The UAV 108 then flies to a sufficiently low altitude suchthat it can safely deliver (e.g., drop) the package including thecustomer's item 102 onto the fiducial 216.

Once the package has been delivered, the UAV 108 flies back to theregional distribution center 114 where it retrieves the next customer'spackage and the delivery process repeats.

In some examples, rather than having a customer print out a fiducial 216for each order, the customer may have a permanent fiducial 216 installedat their location. For example, a customer could install a tile mosaicwhich appears to be decorative but is actually a re-usable andweatherproof fiducial 216 for UAV delivery.

In some examples, the package is connected to a winch on the UAV 108.When the UAV 108 arrives above the fiducial 216, the package is loweredonto the fiducial 216 using the winch. The package is then disconnectedfrom the winch and the winch is retracted before the UAV 108 returns tothe regional distribution center. In some examples, if there is aperson, animal, or some other object which could potentially be harmedby the lowering of the package the UAV 108 will not lower the package.In some examples, the package is not lowered onto the fiducial 216 butis instead lowered onto a visual map point.

In some examples, rather than dropping the package onto the fiducial 216or winching the package down to the fiducial 216, the UAV 108 simplylands on the fiducial 216 and places the package on the fiducial 216.

In general, it is not a strict requirement that the package end updirectly on the fiducial 216. For examples, there may be an acceptablemargin of error (e.g., a 5 ft. radius around the fiducial) for placementof the package on or around the fiducial 216.

In some examples, once the package is delivered, the UAV 108 causes atext message, an email, or some other suitable notification to be sentto the customer, indicating that their package has been delivered.

In some examples, as the UAV 108 travels to the customer's location, theUAV 108 communicates with the regional distribution center such that anestimated time of delivery is continually updated. This estimated timeof delivery can be provided to the user via any number of communicationsmeans (e.g., text message, email, the online retailer's website, and soon).

In some examples, the presence of a fiducial 216 can be used to easilyverify that the delivery location is correct and determine where tosafely leave packages.

Presently, if a person wants to purchase an item, they generally need toeither order the item and wait a number of days for the item to bedelivered or go out to a store and buy the item there. If a person isout of their home, wants the instant gratification of immediatelyobtaining an item, and is unable or unwilling to go to a store, theycurrently have no way of obtaining their item. For example, a personwalking around a city may want to purchase a drink for immediateconsumption but may not have the time or the desire to walk to aconvenience store to purchase the drink. This person would have no wayof obtaining their drink.

Referring to FIGS. 4 and 5 , in some examples, items can be ordered by acustomer 422 using, for example, a mobile device 424 and delivered by anunmanned aerial delivery vehicle 108 (UAV) directly to the customer 422at the location of their mobile device 424 without ever requiring theUAV 108 to land.

When the customer 422 places their order, order information is sent fromtheir mobile device 424 to a retailer 112 and then to a regionaldistribution center 114. In some examples, the order informationincludes an identifier of the ordered item 102 and a location of thecustomer 422 (e.g., a GPS coordinate of the customer 422).

At the distribution center 114, the ordered item 102 is loaded onto adelivery UAV 108 and the customer's GPS coordinate is programmed intothe delivery UAV 108.

Once programmed, the UAV 108 leaves the distribution center 114 andflies toward the GPS coordinate associated with the customer 422. Whenthe UAV 108 reaches the GPS coordinate, the UAV 108 begins to fly aroundthe GPS coordinate in an efficient manner.

At the same time, a validation system included in the UAV 108 searchesfor a validation beacon 426 associated with the customer 422. In someexamples, the validation beacon 426 is a fiducial such as a QR code orbar code displayed on the screen of the customer's mobile device 424. Inthis case, a camera 220 on board the UAV 108 takes still photographs orvideo of the surrounding area as the UAV 108 flies around the GPScoordinate. An image processor processes the photographs or video todetermine whether the fiducial 426 is present in the photographs orvideo. Once the fiducial 426 is detected, the UAV 108 flies toward thefiducial until the UAV 108 is directly above the fiducial 426 (andpresumably the customer 422). The UAV 108 then flies to a sufficientlylow altitude such that the item 102 can be safely delivered to thecustomer 422.

In other examples, the validation beacon is a near-field communicationssignal such as a Bluetooth signal, a WiFi signal, or an infrared signal.In this case, a sensor such as a Bluetooth, WiFi, or infrared sensormonitors the environment as the UAV 108 flies around the GPS coordinate.When the UAV 108 detects the validation beacon signal the UAV 108 fliesin such a way that the received signal strength is maximized. At thispoint the UAV 108 is presumably closest to the customer 422. The UAV 108then flies to a sufficiently low altitude such that the item can besafely delivered to the customer 422.

In some examples, the UAV 108 delivers the package by flying to analtitude where the customer 422 can grab their item from the UAV 108. Insome examples, the package is touch sensitive such that the customer 422can touch the package and trigger a release mechanism on the UAV 108,releasing the package. For example, the package or the payload baymechanism may be provided with a capacitive sensor which triggers arelease mechanism on the UAV 108.

In some examples, rather than directly handing the package to thecustomer 422, the UAV 108 includes a winch which winches the packagedown to the customer 422. Such a winching scheme can increase thedistance between the customer 422 and the UAV 108, thereby increasingthe safety of the transaction. In some examples, if there is a person,animal, or some other object which could potentially be harmed by thelowering of the package, the UAV 108 will not lower the package. In someexamples, the UAV 108 lowers the package onto a point away from but in avicinity of a person.

In some examples, the customer 422 may be on the move and the customer'smobile device 424 can continually update the UAV 108 with the customer'scurrent GPS coordinate. In this way, the customer's location can betracked by the UAV 108 and the customer 422 doesn't have to wait in onelocation for their delivery.

In some examples, the UAV 108 includes an on-board camera 220 whichcaptures still photographs or videos as the UAV 108 flies. When the UAV108 approaches the customer 422 to make its delivery, a people detectionalgorithm analyzes the still photographs or videos and recognizes peoplein the vicinity of the UAV 108. The UAV 108 then plots a flight pathwhich avoids the recognized people. In some examples, the peopledetection algorithm or a facial detection algorithm can be used toidentify the customer 422. For example, the customer 422 provides theretailer 112 with a “selfie” or photograph of the customer 422. When theUAV 108 arrives at the delivery location, the UAV 108 implements facialrecognition and tracking using the on-board camera 220 to identify thecustomer 422. In this way, the UAV 108 can fly to a position near thecustomer 422 and make its delivery, even in a crowd of people. Note thatimage processing and other navigational computation processes can beperformed by the on-board image processor, by a ground station controlsystem, or using land based computing procedurals using remote servers,processors, and databases.

Once the package has been delivered, the UAV 108 flies back to thedistribution center where it retrieves the next customer's package andthe delivery process repeats.

In some examples, a customer 422 may order an item and provide a GPScoordinate, other than their own, to which the item should be delivered.For example, a customer 422 may purchase an item for their friend andprovide their friend's GPS coordinate as the delivery destination. Thefriend is then sent an indication (e.g., an email or a text message)that the item is being delivered to them. When the item arrives, thefriend can validate that the order is for them using any of thevalidation techniques described above (e.g., presenting a QR code ontheir mobile device).

Mappings of street addresses to GPS coordinates are currently inexistence. One example of such a mapping is included in the Google Mapsapplication. These mappings are generally approximate in nature and arenot sufficiently accurate to be useful for automated delivery of itemsto a specific location at an address.

Furthermore, once an automated delivery vehicle (e.g., a UAV 108)reaches a GPS coordinate associated with a customer's address, there isno way to validate that the GPS coordinate is actually associated withthe customer's address.

In this example, existing aerial photography (e.g., satellite imagesfrom, e.g., Google Maps) is used to identify a preferred deliverylocation.

Referring to FIGS. 1 and 6 , when a customer orders an item from, forexample, an online retailer's website, the customer provides a shippingaddress (i.e., the address where they want their item delivered). Thecustomer is also prompted to select a desired delivery location 106 on amap by placing an icon (e.g., a bullseye or an arrow) on an image ofhis/her house 218 derived from aerial or satellite imagery, for example,the icon could be placed in the center of a path, a backyard, adriveway, etc.

Subsequently, at a regional distribution center 114 near the customer'shouse 218, a package including the customer's item is loaded onto a UAV108 (e.g., a multi-rotor UAV) and the UAV 108 is programmed to fly to aGPS coordinate associated with the desired delivery location 106. Insome examples, the GPS coordinate is obtained from a mapping servicesuch as Google Maps.

Once programmed, the UAV 108 leaves the regional distribution center 114attempts to fly to a position above the specified location 106 or anoffset from the specified location 106 and it gets there within theGPS/map registration accuracy. Once the UAV 108 has reached the GPScoordinate associated with the delivery location 106, the UAV 108 isostensibly in range to capture imagery around the delivery location 106.From this point the UAV 108, augments its navigation with visual imageryby comparing its real time imagery (acquired using a camera 220) withthe imagery associated with the user-specified delivery location 106(e.g., Google Maps imagery). For example, the UAV 108 matches featuresin the terrain captured in its real time imagery with features from themap, allowing the UAV 108 to hover over a location that is much closerto the user-specified delivery location 106. The UAV 108 then eitherlands and makes the drop or lowers the package, including the customer'sitem onto the user-specified delivery location 106.

Once the package has been delivered, the UAV 108 flies back to theregional distribution center 114 where it retrieves the next customer'spackage and the delivery process repeats.

In some examples; the SSID associated with the customer's WiFi networkis also programmed into the UAV 108 making it easier to get into rangeto see the delivery location 106. In some examples, WiFi signals emittedby access points in and/or around a customer's house 218 can also beused to accurately deliver an item to a delivery location 106 specifiedby the customer and to validate that the delivery location 106 iscorrect.

In some examples, the customer selects the desired delivery location 106by pointing to it (mouse of touchscreen) on an aerial image.

One advantage of this approach is that using terrain map in addition toa GPS system (and in some cases a WiFi signal) can result in highlyaccurate delivery of the customer's item to a customer designateddelivery location 106.

Another advantage of this approach is that imagery can be used tovalidate that the package is placed where the customer wants it to agreater precision than if GPS alone were used.

In some examples, when the customer places their order, a GPS coordinateassociated with specific location on the customer's property (e.g., thecustomer's doorstep) is provided to the retailer's website. The UAV 108can then deliver the customer's item to this specific location using theabove-described combination of GPS and vision based positioning systems.

In some examples, trees, houses, and large objects can be identifieda-priori, on the map and then used to geo-reference locally at thedelivery site.

As is described above, mappings of street addresses to GPS coordinatessuch as those included in the Google Maps application are generallyapproximate in nature and are not sufficiently accurate to be useful forautomated delivery of items to a specific location at an address. Forsituations where GPS is not sufficiently accurate or is unreliable,companies such as Google, Skyhook, and Navizon have developed. WiFipositioning systems which rely on a mapping of wireless access points toGPS coordinates. In some examples, WiFi positioning systems use thesemappings to triangulate a location of a device (e.g., a smart phone or aUAV) based on a measured received signal strength from a number ofaccess points which are both in the vicinity of the device andrepresented in the mapping.

Furthermore, once an automated delivery vehicle (e.g., a UAV 108)reaches a GPS coordinate associated with a customer's address, there isno way to validate that the GPS coordinate is actually associated withthe customer's address.

To solve these problems, WiFi signals emitted by access points in and/oraround a customer's house 218 can be used to accurately deliver an itemto a location 106 specified by the customer and to validate that thedelivery location 106 is correct.

Referring to FIGS. 1 and 7 when a customer orders an item 102 from, forexample, an online retailer's website, the customer provides a shippingaddress (i.e., the address where they want their item delivered). Insome examples, identifying information related to the customer's WiFinetwork 226 (e.g., the Service Set Identifier (SSID) for their WiFinetwork) is also provided to the retailer's website.

Subsequently, at a regional distribution center 114 near the customer'shouse 218, a package including the customer's item 102 is loaded onto aUAV 108 (e.g., a multi-rotor UAV) and the UAV 108 is programmed to flyto a GPS coordinate associated with the customer's address. In someexamples, the GPS coordinate is obtained from a mapping service such asGoogle Maps which approximately maps GPS coordinates to streetaddresses. In some examples, the SSID associated with the customer'sWiFi network 226 is also programmed into the UAV 108.

Once programmed, the UAV 108 leaves the regional distribution center 114and flies toward the GPS coordinate. Once the UAV 108 has reached theGPS coordinate associated with the customer's address, the UAV 108 isostensibly in range of the WiFi network 226 with identifying information(e.g., SSID) which matches the identifying information provided by thecustomer. At this point, the UAV 108 enables a WiFi signal sensorassociated with a WiFi positioning system in addition to its GPS system.In general, the WiFi positioning system utilizes a mapping of accesspoints associated with surrounding WiFi signals to GPS coordinates topinpoint the UAV's 108 location. In some examples, such a mapping isprovided by a third party such as Google Location Services, Navizon, orSkyHook.

Referring to FIG. 8 , the UAV 108 uses the WiFi positioning system toefficiently move in a direction toward the WiFi signal associated withthe SSID provided by the customer (and presumably toward their actualaddress). At some point (e.g., when it is determined that the receivedsignal strength of the customer's WiFi signal is above a threshold) theUAV 108 is considered to be at the delivery location 106 at thecustomer's address. At this point the UAV 108 flies to a sufficientlylow altitude such that it can safely deliver (e.g., drop) the packageincluding the customer's item 102 onto the customer's lawn.

Once the package has been delivered, the UAV 108 flies back to theregional distribution center 114 where it retrieves the next customer'spackage and the delivery process repeats.

One advantage of this approach is that using a WiFi positioning systemin addition to a GPS system can result in highly accurate delivery ofthe customer's item to the customer's location.

Another advantage of this approach is that an SSID of the customer'swireless network 226 (provided by the customer) can be used to validatethat the UAV 108 is delivering the customer's item to the customer'saddress.

In some examples, when the customer places their order, a GPS coordinateassociated with specific location on the customer's property (e.g., thecustomer's doorstep) is provided to the retailer's website. The UAV 108can then deliver the customer's item to this specific location using theabove-described combination of GPS and WiFi positioning systems.

In some examples, rather than determining the customer's GPS coordinatesfrom a service such as Google maps, the customer's GPS coordinates arcdetermined by consulting a database which maps identifying informationof WiFi networks 226 (e.g., SSIDs) to GPS coordinates. In particular,such a database is searched for the SSID associated with the customer'sWiFi network 226 and, if found, the GPS coordinate associated with theSSID is used as the delivery coordinate.

In some examples, as the UAV 108 travels around the regionaldistribution center delivering packages, the UAV 108 monitors WiFinetworks in the area to create its own database relating WiFi networksand GPS coordinates. This database can be used in conjunction with theWiFi positioning system described above.

Even with the advent of electronic communications such as email textmessaging, there is still a need for communication via paper. One commonexample is a document (e.g., a contract) which requires originalsignatures. The completion of such documents is often a time sensitivematter, requiring the signing of the document to be completed in amatter of hours.

While delivery using email or text message is nearly instantaneous, anoriginal signature cannot be transmitted using these technologies.Conversely, original signatures can be obtained using services such asthe U.S. Postal Service, FedEx, or UPS. However, these servicesgenerally take one or more days to deliver documents (even if thedocuments only need to be delivered across a city).

For this reason, courier services (e.g., bicycle couriers, automobilecouriers, and so on) exist. These services involve a human retrieving asmall package or document from a sender and quickly delivering thedocument to a recipient (usually within a small geographic area such asa city). Use of such courier services can be expensive and, since theyinvolve humans, can result in mistakes due to human error.

To overcome some of the drawbacks of using courier services, UnmannedAerial Vehicles (UAVs) can be used as couriers, delivering documents andsmall packages between locations within a small geographic area.

Referring to FIG. 9 , a UAV 108 (e.g., a multi-rotor unmanned aerialvehicle) is parked on a first base station 928 on a roof of a firstbuilding 930. A second building 932 has a second base station 934 on itsroof. In some examples, each of the base stations 928, 934 includes afiducial (e.g., a QR code or a bar code) which is visible from theairspace above the base station. Note that the aerial vehicle can belaunched from a stationary or moving vehicle and hand on such a vehicleusing an array of beacons to automatically orient the vehicle to ahandling surface.

At some point, a first person in the first building 930 needs a documentor small package to be delivered to a second person in the secondbuilding 932. The first person has their document or package attached tothe UAV 108 and indicates to the UAV 108 that the package should bedelivered to a person at the second building 932. In some examples, thefirst person provides an address for delivery and a computer programcalculates an approximate GPS coordinate corresponding to the addressusing a mapping application such as Google Maps.

Referring to FIG. 10 , once the package is attached to the UAV 108 andthe approximate delivery GPS coordinate is programmed into the UAV 108,the UAV 108 launches from the first base station 928 and flies towardthe GPS coordinate associated with the delivery location (i.e., thesecond building 932). When the UAV 108 reaches the GPS coordinate, theUAV 108 begins to fly around the GPS coordinate in an efficient manner.At the same time, a camera on board the UAV 108 is activated and beginstaking still photographs or video of the surrounding area. An imageprocessor processes the photographs or video to determine whether thefiducial associated with the second building 932 is present in thephotographs or video. Once the fiducial is detected, the UAV 108 fliestoward the fiducial and lands on the second base station 934 which isassociated with the fiducial.

The UAV 108 then causes a delivery notice (e.g., an email or a textmessage) to be sent to the second person in the second building 932,indicating that they should retrieve their document or package. Thesecond person then retrieves their document or package, completing thedelivery.

In some examples, the base stations on each of the buildings include acharger for the UAV. In such examples, the UAV 108 may stay on the basestation 934 of the second building 932, charging its batteries as itwaits for its next courier assignment. In other examples, the UAV 108may charge its batteries to ensure that it can safely return to thefirst building 930 where it waits for its next courier assignment.

In some examples, the base stations on each of the buildings include aweather station to monitor the weather. The weather informationcollected by the base stations can be used to determine whether it issafe for the UAV 108 to fly from one building to the other.

In some examples, other types of fiducials can be used to accuratelyland the UAV 108 on a base station. For example, visible or infraredlight fiducials can be used.

Referring to FIG. 11 , in some examples, to ensure that the item 102being delivered isn't damaged by being dropped from an excessive height,the UAV 108 drops the item 102 into a receptacle 604 including adecelerating slide 606 and a container 1601. When the item 102 isdropped into an open end 612 of the decelerating slide 606, the item 102is slowly decelerated as it travels along a gradual bend in thedecelerating slide 606. After passing through the decelerating slide606, the item is deposited into the container 610 where it can beretrieved by a customer.

Referring to FIG. 12 , in some examples, to ensure that the item 102being delivered isn't damaged by being dropped from an excessive height,the UAV 108 drops the item 102 into a net-like structure 714 whichcatches and safely decelerates the item 102 before it hits the ground.

In some examples, to ensure that the item 102 being delivered isn'tdamaged by being dropped from an excessive height, items may be packagedusing packing materials and/or methods which prevent damage due toimpact with the ground or other items. For example, products may bepackaged such that they are surrounded on all sides by airbags,Styrofoam, honeycombed cardboard, or other cushioning materials.

FIG. 13 is a flowchart 1300 of a first exemplary UAV delivery to alocation. At operation 1302, a customer orders an item and provides ashipping address. At operation 1304, a retailer provides the customerwith, for example, a printable fiducial. The retailer instructs thecustomer to print the fiducial and place it outdoors in a location wherethe customer wants the item to be delivered. In some examples, ratherthan having a customer print out a fiducial for each order, the customermay have a permanent fiducial installed at their location. At operation1306, the customer places the fiducial at their location, either byprinting the fiducial and placing the fiducial in a location outside oftheir house or installing the fiducial in a location outside of theirhouse.

At operation 1308, the UAV leaves a regional distribution center withthe customer's item and flies toward the GPS coordinate associated withthe customer's shipping address. At operation 1310, the UAV reaches theGPS coordinate and fly around the GPS coordinate in an efficient mannerto identify the fiducial. For example, a camera on board the UAV isactivated and begins taking still photographs or video of thesurrounding area. An image processor processes the photographs or videoto determine whether the fiducial is present in the photographs orvideo.

At operation 1312, the UAV detects the fiducial is detected. Atoperation 1314, the UAV delivers the customer's item at or near thefiducial. For example, the UAV flies directly above the fiducial. TheUAV then flies to a sufficiently low altitude such that it can safelydeliver (e.g., drop) a package including the customer's item onto thefiducial. In some examples, the package is connected to a winch on theUAV. When the UAV arrives above the fiducial, the package is loweredonto the fiducial using the winch. The package is then disconnected fromthe winch and the winch is retracted before the UAV returns to theregional distribution center. In some examples, the UAV simply lands onthe fiducial and places the package on the fiducial.

FIG. 14 is a flowchart 1400 of a second exemplary UAV delivery to alocation. At operation 1402, the UAV leaves a distribution center with acustomer's item and flies toward a GPS coordinate programmed into theUAV and associated with the customer. When the UAV reaches the GPScoordinate, the UAV begins to fly around the GPS coordinate in anefficient manner.

At operation 1404, a validation system included in the UAV searches fora validation beacon associated with the customer. At operation 1406, inone embodiment, the validation beacon is a fiducial such as a QR code orbar code displayed on a screen of the customer's mobile device. A cameraon board the UAV takes still photographs or video of the surroundingarea as the UAV flies around the GPS coordinate. An image processorprocesses the photographs or video to determine whether the fiducial ispresent in the photographs or video. Once the fiducial is detected, theUAV flies toward the fiducial until the UAV is directly above thefiducial (and presumably the customer). At operation 1408, in anotherembodiment, the validation beacon is a near-field communications signalsuch as a Bluetooth signal, a WiFi signal, or an infrared signal. Asensor such as a Bluetooth, WiFi, or infrared sensor monitors theenvironment as the UAV flies around the GPS coordinate. The UAV detectsthe validation beacon signal the UAV flies in such a way that thereceived signal strength is maximized.

At operation 1410, UAV detects the validation beacon, as describedabove. At operation 1412, the UAV delivers the item to the customer. Forexample, the UAV flies to a sufficiently low altitude such that the itemcan be safely delivered to the customer.

FIG. 15 is a flowchart 1500 of a third exemplary UAV delivery to alocation. At operation 1502, a customer select a desired deliverylocation on a map by, for example, placing an icon (e.g., a bullseye oran arrow) on an image of his/her house derived from aerial or satelliteimagery. At operation 1504, a UAV with a package including thecustomer's item is programmed to fly to a GPS coordinate associated withthe desired delivery location. The UAV leaves the regional distributioncenter and travels to GPS/map location.

At operation 1506, the UAV reaches the GPS coordinate associated withthe delivery location and is ostensibly in range to capture imageryaround the delivery location. At operation 1508, the UAV augments itsnavigation with visual imagery by comparing its real time imagery(acquired using a camera) with the imagery associated with theuser-specified delivery location, allowing the vehicle to hover over alocation that is much closer to the user-specified delivery location.

At operation 1510, the UAV delivers the package to the customer byeither landing and dropping the package onto the user-specified deliverylocation or lowering the package including the customer's item onto theuser-specified delivery location.

FIG. 16 is a flowchart 1600 of a fourth exemplary UAV delivery to alocation. At operation 1602, a customer orders an item from, forexample, an online retailer's website and provides to the retailer'swebsite a shipping address and identifying information related to thecustomer's WiFi network (e.g., the Service Set Identifier (SSID) fortheir WiFi network). In some embodiments, at operation 1604, thecustomer's GPS coordinates are determined by consulting a database whichmaps identifying information of WiFi networks (e.g., SSIDs) to GPScoordinates. For example, the database is searched for the SSIDassociated with the customer's WiFi network and, if found, the GPScoordinate associated With the SSID is used as the delivery coordinate.

At operation 1606, the SSID associated with the customer's WiFi networkis programmed into the UAV making it easier to get into range to see thedrop-off location. In some examples, WiFi signals emitted by accesspoints in and/or around a customer's house can also be used toaccurately deliver an item to a location specified by the customer andto validate that the delivery location is correct. At operation 1608,the UAV reaches the GPS coordinate associated with the customer'saddress and is ostensibly in range of the WiFi network with identifyinginformation (e.g., SSID) which matches the identifying informationprovided by the customer.

At operation 1610, the UAV enables a WiFi signal sensor associated witha WiFi positioning system in addition to its GPS system. The UAV usesthe WiFi positioning system to efficiently move in a direction towardthe WiFi signal associated with the SSID provided by the customer (andpresumably toward their actual address). At operation 1612, the UAV isconsidered to be at the delivery location at the customer's addresswhen, for example, it is determined that a received signal strength ofthe customer's WiFi signal is above a threshold. At operation 1614, theUAV flies to a sufficiently low altitude such that it can safely deliver(e.g., drop) the package including the customer's item onto thecustomer's lawn.

FIG. 17 is a flowchart 1700 of a fifth exemplary UAV delivery to alocation. At operation 1702, the UAV is located on a first base stationon a roof of a first building. In some examples, each base stationincludes a fiducial (e.g., a QR code or a bar code) which is visiblefrom the airspace above the base station.

At operation 1704, an item (i.e., a document or package) is attached tothe UAV and indicates to the UAV that the package should be delivered toa second person at a second building. In some examples, a first personprovides an address for delivery and a computer program calculates anapproximate GPS coordinate corresponding to the address using a mappingapplication such as Google Maps.

At operation 1706, the UAV launches from the first base station andflies toward the GPS coordinate associated with the delivery location(i.e., the second building). At operation 1708, when the UAV reaches theGPS coordinate, the UAV begins to fly around the GPS coordinate in anefficient manner and a camera on board the UAV is activated and beginstaking still photographs or video of the surrounding area. An imageprocessor processes the photographs or video to determine whether thefiducial associated with the second building is present in thephotographs or video. At operation 1710, once the fiducial is detected,the UAV flies toward the fiducial and lands on the second base stationwhich is associated with the fiducial.

At operation 1712, the UAV causes a delivery notice (e.g., an email or atext message) to be sent to the second person in the second building,indicating that they should retrieve their document or package. Atoperation 1714, the second person then retrieves their document orpackage, completing the delivery.

In some examples, other types of fiducials can be used to accuratelyland the UAV on the base station. For example, visible or infrared lightfiducials can be used.

Amazon, Matternet, CyPhy Works and others have suggested the use offlying drones for package delivery. These drone prototypes have beenportrayed as having a conventional multi-rotor configuration. One of themain technological challenges of this idea is the limited range,endurance and payload that current battery technology imposes onconventional multi-rotor vehicles. In some examples, enhancing theseparameters to the point where the use of multi-rotor vehicles ispractical requires a redesign of the multi-rotor configuration.

FIG. 18A-18C illustrate three hybrid multicopter configurations: FIG.18A illustrates a multicopter without a propeller or an extended liftingsurface. FIG. 18B illustrates a multicopter with a propeller but withoutan extended lifting surface. FIG. 18C illustrates a multicopter with apropeller and an extended lifting surface. FIG. 18C uses a propeller inthe vertical plane for propulsion and an extended lifting surface tosupplement the rotors in forward flight. Each configuration includes anaerodynamic body 1802, struts 1804, and rotors 1806. There is a primaryaxis 1808 of the multicopter in forward flight mode. The struts 1804 aregenerally orthogonal to the primary axis 1808. The body 1802 and struts1804 can have an aerodynamic shape with respect to the primary axis 1808for direction of movement. FIGS. 18B and 18C includes a propeller 1810.FIG. 18C includes a wing 1812. In additional embodiments, FIG. 18C mayinclude additional smaller wings 1814. The configurations enhance therange of a standard multi-copter configuration to be used, for example,in a package delivery scenario.

The multicopter can be steered using hovering rotors 1806, which can beselectively oriented or can be used with flight control surfaces on thespars or wings of the UAV to adjust the direction of flight.

In some embodiments, the wing 1812 includes one or more flaps 1816. Theflaps 1816 are used to increase the lift of the wing 1812, and aremounted on the wing 1816 trailing edges. Steering of the multicopter iscontrolled using the one or more flaps 1816 and/or the rotors 1806. Theflaps 1816 may be of a difference size, shape, and/or location than asillustrated in FIG. 18C. In further embodiments, the multicopterincludes an inertial measurement unit (IMU) for automated flight controlbased on direction and, in combination with the one or more flaps 1816and/or the rotors 1806, to compensate for environmental factors, such ascross-winds.

The analysis presented is founded on rotor momentum theory applied toforward flight and standard helicopter and airplane performance theory.The configurations take advantage of the fact that a rotor in forwardflight requires less power to generate a given amount of thrust than inhover, and that lifting surfaces are more efficient at producing liftthan rotors.

FIG. 18D illustrate a multicopter with rotors in a forward flightorientation. Conventional helicopters and multicopters need to tilttheir rotors forward to provide a propulsive force to counteract thedrag in addition to produce the lift necessary for the weight of theUAV.

FIG. 18E illustrates a plot representing the theoretical behavior of amulticopter propeller for an exemplary multicopter. The plot shows thatthe induced power at fast forward flight can be a fraction (down to 40%,for example) of the induced power at hover when the rotor is operatingat an effective inclination of 0 degrees. As the rotor inclinationincreases from 0 to higher angles, the induced power (power required forthrust generation) follows the trends shown on the plot, where P/P_(h)is the ratio of forward flight power vs. power required to hover.

Measured data from an exemplary multicopter airframe showed that avehicle inclination of ˜15 degree was needed to achieve un-acceleratedlevel forward flight at a velocity of 25 Knots.

The lifting surface is a good complement to the approach, consideringthat flight surfaces such as wings are much more efficient at producinglift than rotors. However, considering that a key design constraint arcthe overall vehicle dimensions, it is desired to have a design thatminimizes the wingspan. Ideally, in this example, the wingspan does notextend beyond the rotors. This results in a wing with a low aspect ratiothat is able only to produce a fraction of the lift necessary tocounteract the vehicle weight.

In the model used for the calculations presented in FIGS. 18A-18J, awing with a span of 1.5 m (5˜ft) and an aspect ratio of 4 is used toillustrate the system parameters. Realistic aerodynamic airfoil and wingperformance values were used based on a simple vortex lattice model. Insome embodiments, the wing can be at least partially stowed to theairframe.

FIG. 18F illustrates a plot representing a performance of a simplemulticopter design. The performance of the simple multicopter design isthe baseline to which the other two approaches (a multicopter with apropeller and without an extended lifting surface, and a multicopterwith a propeller and an extended lifting surface) are compared. The plotshows the estimated power predictions for a vehicle inclination of 14degrees with a GTOW of 100 N. At 25 Knots forward speed, the systemrequires about 1540 W. Note the very shallow reduction in the inducedpower with forward flight (line 1820). At this inclination the benefitsof forward flight in terms of power saving with respect to hover aremarginal.

A multicopter configuration faces steep challenges in order to achievehigh forward flight speeds that can compete with a fixed wing aircraft.Generally, there is a substantial drag increase when tilting thevehicle, large multicopters aren't commonly designed to be streamlinedand efficient in forward flight.

FIG. 18G illustrates a simple analytical model implemented to calculatethe power requirements of a hex-copter with a drive propeller and ashorter wing. A small wing with a span of 1.5 m, an aspect ratio of 4,and realistic aerodynamic parameters was assumed. The nominal weight ofthe vehicle was assumed to be 102 N (˜23 lb) which is around theexpected Gross Take Off Weigh (GTOW) of the multicopter with a 5 lbpayload.

The total power of the aircraft in cruise is calculated by adding theinduced, profile and parasitic powers. For maximum range in the case ofan aircraft with a drive propeller and no extended lifting surface suchas a wing a power consumption of ˜1350 W at 35 knots is expected.

FIG. 18H-I illustrates a multicopter with a drive propeller and wing,including an aerodynamic extended lifting surface resulting in areduction in the thrust requirements of the rotors during cruise. Thisresultant lower disk loading results in higher aerodynamic efficiency.The lift generated by the wing adds a new drag term to the force balanceequation and increases the overall mass of the system. The analysisshows that drag and mass penalties are largely outweighed by the overallreduction in power at cruising speed.

Assuming a weight increase of ION (2.25 lb) with the wing, the systemneed to cruise at 35 knots to achieve level unaccelerated flight, andconsumes about 965 W. This is a reduction in power of 385 W.

FIG. 18J illustrates a table representing the mass, hover, and cruisepower for the three configurations described above. These idealizedrange calculations do not take into account all the factors in astandard mission profile, (takeoff, package drop off, and landing);rather, a continuous ideal cruise condition at a constant mass wasassumed to illustrate the flight parameters.

This analysis assumes a vehicle with a battery capacity of 480 Wh (21.8Ah, 22.2V) with a mass of 2800 g (6.2 lb), this is typical for acurrently available lithium polymer battery. The parameters that definethe aerodynamics of the system were chosen to approximate performancewith enough resolution to identify trends and overall orders ofmagnitude. It is evident that use of at least one drive propeller (thatis, a propeller configured to provide thrust in a forward axialdirection along a propulsion axis of the UAV) and/or at least oneextended lifting surface such as a wing increases range.

Referring to FIGS. 19 and 20 , a first exemplary multi-rotor UAV 1102includes an airframe 1100 which facilitates operation of the UAV 1102 intwo modes: a multi-copter mode (FIG. 19 ) and a forward flight mode(FIG. 20 ). To enable the two modes of operation, the airframe includesa streamlined fuselage 1100 which is aerodynamically optimized such thatit reduces the drag in forward flight while simultaneously working as alifting surface. The fuselage 1100 is surrounded by an array of an evennumber of rotors 1106 (e.g., 4, 6, 8, or 10) that tilt back and forthwhen switching between multi-copter mode and forward flight mode. Forexample, referring to FIG. 19 , in multi-copier mode the rotors 1106 areall in a substantially horizontal configuration (i.e., substantiallyparallel to the ground) allowing for vertical take-off and landing,hovering, and low speed flight. Referring to FIG. 20 , to convert toforward flight mode, at least some of the rotors 1106 tilt or rotatesuch that they are in a substantially vertical configuration (i.e.,substantially perpendicular to the ground) allowing for higher speedforward flight.

In some examples, when the at least some rotors 1106 tilt or rotate froma substantially vertical configuration into a substantially horizontalconfiguration, the lifting surfaces on the spars 1103 connecting the atleast some rotors 1106 to the center of the fuselage 1100 rotate from asubstantially horizontal configuration into a substantially verticalconfiguration. Similarly, when the at least some rotors 1106 tilt orrotate from a substantially horizontal configuration into asubstantially vertical configuration, the lifting surfaces on the spars1103 rotate from a substantially vertical configuration to asubstantially horizontal configuration.

In other examples, when the at least some rotors 1106 tilt or rotatebetween a substantially vertical configuration and a substantiallyhorizontal configuration, the lifting surfaces on the spars 1103 of theat least some rotors 1106 remain in a substantially horizontalconfiguration.

In operation, the UAV 1102 performs vertical takeoffs and landings(e.g., when hovering to perform package delivery) in multi-copter modeand then switches to forward flight mode (i.e., tilted rotorconfiguration) when flying over longer distances. The faster speeds andreduced power consumption associated with forward flight mode allow theUAV 1102 to achieve a greater range and endurance than would be possibleusing a conventional multi-copier.

In some examples, the UAV 1102 includes a large internal volume than canhold a payload. For example, the streamlined fuselage 1100 may include apackage bay 1104 that holds a payload either by enclosing it on theinside or making the surface of the package part of the fuselage 1100itself. In some examples, the package bay is inside of the fuselage 1100to ensure that the streamlined aerodynamics of the fuselage 1100 arepreserved.

Referring to FIG. 21 in another configuration, the UAV 1102 includes astreamlined fuselage 1100 including five spars 1103 extending from acentral package bay 1104. A number (i.e., four in this case) of thespars 1103 each include a rotor 1106 mounted in a substantiallyhorizontal position relative to the ground for providing vertical thrustfor the UAV 1102. One (or more) of the spars 1103 includes a rotor 1107mounted in a substantially vertical position relative to the ground forproviding horizontal thrust for the UAV 1102.

Referring to FIG. 22 , in operation, when hovering or traveling overshort distances, the rotors 1106 that are mounted in a substantiallyhorizontal position arc used primarily, with the rotor 1107 mounted in asubstantially vertical position being used little, if at all. Whentraveling over longer distances, the rotor 1107 mounted in asubstantially vertical position relative to the ground acts as apropeller, moving the UAV 1102 in a lateral direction, with thestreamlined fuselage 1100 providing lift (i.e., the UAV 1102 ‘flies’like an airplane). When flying like an airplane, the UAV 1102 may usethe rotors 1106 mounted in a horizontal position to provide additionallift, if necessary.

Referring to FIG. 23 , in some examples, the spar 1103 that thehorizontally mounted rotor 1107 is mounted upon is rotatable relative tothe other spars 1103 of the UAV 1102. The spar 1103 may be rotated toalter the flight characteristics of the UAV 1102 and/or when the UAV1102 switches between a hovering and a flying mode.

Referring to FIG. 24 , a second exemplary multi-rotor UAV helicopter1000 includes a central body 1002 from which a number (i.e., n) of rigidspars 1004 radially extend. The end of each rigid spar 1004 includes athruster 1006 rigidly mounted thereon. In some examples, each of thethrusters 1006 includes an electric motor 1008 (e.g., a brushless DCmotor) which drives a rotor 1010 to generate thrust. Very generally, inoperation the central body 1002 includes a power source which providespower to the motors 1008 which in turn cause the rotors 1010 to rotate.While rotating, each of the rotors 1010 forces air above the helicopter1000 in a generally downward direction to generate a thrust having amagnitude and direction that can be represented as a thrust vector 1012.

Referring to FIG. 25 , in contrast to conventional multi-rotorhelicopter configurations, the multi-rotor helicopter 1000 of FIGS. 23and 24 has each of its thrusters 1006 rigidly mounted with both adihedral angle, θ and a twist angle, ϕ. In some examples, both (1) thedihedral angle is the same for each spar 1004, and (2) the magnitude ofthe twist angle is the same for each spar 1004 with the sign of thetwist angle being different for at least some of the spars 1004. Tounderstand the mounting angles of the thrusters 1006, it is helpful toconsider the plane defined by the rigid spars 1004 of the multi-rotorhelicopter 1000 as being a horizontal plane 2014. With this in mind,mounting the thrusters 1006 with a dihedral angle includes mounting thethrusters 1006 at an angle, θ with respect to a line from the center ofthe rotor 1010 to the center of the central body 1002. Mounting athruster 1006 with a twist angle at the end of a rigid spar 1004includes mounting the thrusters 1006 at an angle, ϕ such that they arerotated about a longitudinal axis of the rigid spar 1004.

Due to the dihedral and twist mounting angles of the thrusters 1006, thethrust vectors 1012 are not simply perpendicular to the horizontal plane2014 defined by the rigid spars 1004 of the multi-rotor helicopter 1000.Instead, at least some of the thrust vectors 1012 have a direction withan oblique angle to the horizontal plane 2014. The thrust force vectors,

are independent (i.e., no force vector is a multiple of other of theforce vectors) or there are at least k (e.g., k=3,6, etc.) independentthrust force vectors.

Referring to FIG. 26 , a detailed view of an i^(th) thruster 1006 showstwo different coordinate systems: an x, y, z coordinate system and au_(i), v_(i), w_(i) coordinate system. The x, y, z coordinate system isfixed relative to the vehicle and has its z axis extending in adirection perpendicular to the horizontal plane defined by the rigidspars 1004 of the multi-rotor helicopter 1000. The x and y axes extendin a direction perpendicular to one another and parallel to thehorizontal plane defined by the rigid spars 1004. In some examples, thex, y, z coordinate system is referred to as the “vehicle frame ofreference.” The u_(i), v_(i), w_(i) coordinate system has its w_(i) axisextending in a direction perpendicular to a plane defined by therotating rotor 1010 of the i^(th) thruster 1006 and its u_(i) axisextending in a direction along the i^(th) spar 1004. The u_(i) and v_(i)axes extend in a direction perpendicular to one another and parallel tothe horizontal plane defined by the rotating rotor 1010. In someexamples, the u_(i), v_(i), w_(i) coordinate system is referred to asthe “rotor frame of reference.” Note that the x, y, z coordinate systemis common for all of the thrusters 1006 while the u_(i), v_(i), w_(i) isdifferent for each (or at least some of) the thrusters 1006.

The rotational difference between the x, y, z and the u_(i), v_(i),w_(i) coordinate systems for each of the n thrusters 1006 can beexpressed as a rotation matrix R_(i). In some examples, the rotationmatrix R_(i) can be expressed as the product of three separate rotationmatrices as follows:R _(i) =R _(i) ^(φ) R _(i) ^(θ) R _(i) ^(ϕ)where R_(i) ^(φ) is the rotation matrix that accounts for the rotationof the i^(th) spar relative to the x, y, z coordinate system, R_(i) ^(θ)is the rotation matrix that accounts for the dihedral angle, θ relativeto the x, y, z coordinate system, and R_(i) ^(ϕ) is the rotation matrixthat accounts for the twist angle, ϕ relative to the x, y, z coordinatesystem.

Very generally, multiplying an arbitrary vector in the u_(i), v_(i),w_(i) coordinate system by the rotation matrix R_(i) results in arepresentation of the arbitrary vector in the x, y, z coordinate system.As is noted above, the rotation matrix R_(i) at the i^(th) spar dependson the spar number, i, the dihedral angle, θ, and the twist angle, ϕ.Since each spar has its own unique spar number, i, dihedral angle, θ,and twist angle, ϕ each spar has a different rotation matrix, R_(i). Oneexample of a rotation matrix for a second spar with a dihedral angle of15 degrees and a twist angle of −15 degrees is

$\begin{bmatrix}{{0.4}830} & {{- {0.8}}700} & {{- {0.0}}991} \\{{0.8}365} & {{0.4}250} & {{0.3}459} \\{- 0.2588} & {{- {0.2}}500} & {{0.9}330}\end{bmatrix}\quad$

In general, the ith thrust vector 1012 can be represented as a forcevector,

113. The force vector,

113 generated by the ith thruster 1006 extends only along the w_(i) axisof the coordinate system for the ith thruster 1006. Thus, the ith forcevector 1013 can be expressed as:

$= \begin{bmatrix}0 \\0 \\f_{i}\end{bmatrix}$where f_(i) represents the magnitude of the i^(th) force vector 1013along the w_(i) axis of the u_(i), v_(i), w_(i) coordinate system. Insome examples, f_(i) is expressed as:f _(i) ≈k ₁ω_(i) ²where k₁ is an experimentally determined constant and ω_(i) ² is thesquare of the angular speed of the motor 1008.

The components of i^(th) force vector 1013 in the x, y, z coordinatesystem can be determined by multiplying the i^(th) force vector 1013 bythe i^(th) rotation matrix R_(i) as follows:

$= {{R_{i}} = {R_{i}\begin{bmatrix}0 \\0 \\f_{i}\end{bmatrix}}}$where

is a vector representation of the i^(th) force vector 1013 in the x, y,z coordinate system.

The moment due to the i^(th) thruster 1006 includes a motor torquecomponent due to the torque generated by the thruster's motor 1008 and athrust torque component due to the thrust generated by the rotor 1010 ofthe thruster 1006. For the i^(th) thruster 1006, the motor rotates aboutthe w_(i) axis of the u_(i), v_(i), w_(i) coordinate system, generatinga rotating force in the u_(i), v_(i) plane. By the right hand rule, themotor torque generated by the i^(th) thruster's motor 1008 is a vectorhaving a direction along the w_(i) axis. The motor torque vector for thei^(th) thruster can be expressed as:

$= \begin{bmatrix}0 \\0 \\\tau_{i}\end{bmatrix}$whereτ_(i) ≈k ₂ω_(i) ²,with k₂ being an experimentally determined constant, and ω_(i) ² beingthe square of the angular speed of the motor 1008.

To express the motor torque vector in the x, y, z coordinate system, themotor torque vector is multiplied by the rotation matrix R_(i) asfollows:

$= {{R_{i}} = {R_{i}\begin{bmatrix}0 \\0 \\\tau_{i}\end{bmatrix}}}$

The torque due to the thrust generated by the rotor 1010 of the i^(th)thruster 1006 is expressed as the cross product of the moment arm of thei^(th) thruster 1006 in the x, y, z coordinate system,

and the representation of the i^(th) force vector 1013 in the x, y, zcoordinate system,

:

=

×

where the moment arm is expressed as the length of the i^(th) spar 1004along the u_(i) axis of the u_(i), v_(i), w_(i) coordinate systemmultiplied by the spar rotation matrix, R_(i) ^(φ).

$= {R_{i}^{\varphi}\begin{bmatrix}\ell \\0 \\0\end{bmatrix}}$

The resulting moment due to the i^(th) thruster 1006 can be expressedas:

$= {{\overset{\_}{T_{1i}^{xyz}} +} = {{R_{i}\begin{bmatrix}0 \\0 \\\tau_{i}\end{bmatrix}} + {{R_{i}^{\varphi}\begin{bmatrix}\ell \\0 \\0\end{bmatrix}} \times {R_{i}\begin{bmatrix}0 \\0 \\f_{i}\end{bmatrix}}}}}$

The force vectors in the x, y, z coordinate system,

generated at each thruster 1006 can be summed to determine a net thrustvector:

$= {{\sum\limits_{i = 1}^{n}} = {\sum\limits_{i = 1}^{n}{R_{i}\begin{bmatrix}0 \\0 \\f_{i}\end{bmatrix}}}}$

By Newton's second law of motion, a net translational accelerationvector for the multi-rotor helicopter 1000 can be expressed as the netforce vector in the x, y, z coordinate system,

divided by the mass, m of the multi-rotor helicopter 1000. For example,for a multi-rotor helicopter 1000 with n thrusters, the nettranslational acceleration vector can be expressed as:

a ¯ ⁢ = . ⁢ m = 1 m ⁢ ∑ i = 1 n ⁢ R i ⁡ [ 0 0 f i ]

The moments in the x, y, z coordinate system,

generated at each thruster 1006 can be summed to determine a net moment:

$= {{\sum\limits_{i = 1}^{n}} = {\sum\limits_{i = 1}^{n}\left( {{R_{i}\ \begin{bmatrix}0 \\0 \\\tau_{i}\end{bmatrix}} + {{R_{i}^{\varphi}\ \begin{bmatrix}\ell \\0 \\0\end{bmatrix}} \times {R_{i}\begin{bmatrix}0 \\0 \\f_{i}\end{bmatrix}}}} \right)}}$

By Newton's second law of motion, a net angular acceleration vector forthe multi-rotor helicopter 1000 can be expressed as the sum of themoments due to the n thrusters divided by the moment of inertia, J ofthe multi-rotor helicopter 1000. For example, for a multi-rotorhelicopter 1000 with n thrusters, the net angular acceleration can beexpressed as:

α _ = J = 1 J ⁢ ∑ i = 1 n ⁢ ( R i ⁡ [ 0 0 τ i ] + R i φ ⁡ [ ℓ 0 0 ] × R i ⁡ [0 0 f i ] )

Based on the above model of the multi-rotor helicopter 1000, it shouldbe apparent to the reader that the magnitudes and directions of theoverall translational acceleration vector

and the overall angular acceleration vector

can be individually controlled by setting appropriate values for theangular speeds, ω_(i) for the motors 1008 of each of the n thrusters1008.

Referring to FIG. 27 , in an exemplary approach to controlling amulti-rotor helicopter 1000, a multi-rotor helicopter control system4000 receives a control signal 4016 including a desired position

, in an inertial frame of reference (specified as an n, w, h (i.e.,North, West, height) coordinate system (where the terms “inertial frameof reference” and n, w, h coordinate system are used interchangeably),and a desired rotational orientation

, in the inertial frame of reference (specified as a roll (R), pitch(P), and yaw (Y) in the inertial frame of reference), and generates avector of voltages

used to drive the thrusters 1008 of the multi-rotor helicopter 1000 tomove the multi-rotor helicopter 1000 to the desired position in spaceand the desired rotational orientation.

The control system 4000 includes a first controller module 4018, asecond controller module 4020, an angular speed to voltage mappingfunction 4022, a plant 4024 (i.e., the multi-rotor helicopter 1000), andan observation module 4026. The control signal 4016, which is specifiedin the inertial frame of reference is provided to the first controller4018 which processes the control signal 4016 to determine a differentialthrust force vector, Δ

, and a differential moment vector, Δ

, each specified in the frame of reference of the multi-rotor helicopter1000 (i.e., the x, y, z coordinate system). In some examples,differential vectors can be viewed as a scaling of a desired thrustvector. For example, the gain values for the control system 4000 may befound using empiric tuning procedures and therefore encapsulates ascaling factor. For this reason, in at least some embodiments, thescaling factor does not need to be explicitly determined by the controlsystem 4000. In some examples, the differential vectors can be used tolinearize the multi-rotor helicopter system around a localized operatingpoint.

In some examples, the first controller 4018 maintains an estimate of thecurrent force vector and uses the estimate to determine the differentialforce vector in the inertial frame of reference, Δ

, as a difference in the force vector required to achieve the desiredposition in the inertial frame of reference. Similarly, the firstcontroller 4018 maintains an estimate of the current moment vector inthe inertial frame of reference and uses the estimate to determine thedifferential moment vector in the inertial frame of reference, Δ

, as a difference in the moment vector required to achieve the desiredrotational orientation in the inertial frame of reference. The firstcontroller 4018 then applies a rotation matrix to the differential forcevector in the inertial frame, Δ

, to determine its representation in the x, y, z coordinate system ofthe multi-rotor helicopter 1000, Δ

. Similarly, the first controller 4018 applies the rotation matrix tothe differential moment vector in the inertial frame of reference, Δ

, to determine its representation in the x, y, z coordinate system ofthe multi-rotor helicopter 1000, Δ

.

The representation of the differential force vector in the x, y, zcoordinate system, Δ

, and the representation of the differential moment vector in the x, y,z coordinate system, Δ

, are provided to the second controller 4020 which determines a vectorof differential angular motor speeds:

${\Delta\overset{¯}{\omega}} = \begin{bmatrix}{\Delta\omega}_{1} \\{\Delta\omega}_{2} \\\vdots \\{\Delta\omega}_{n}\end{bmatrix}$

As can be seen above, the vector of differential angular motor speeds, Δ

, includes a single differential angular motor speed for each of the nthrusters 1006 of the multi-rotor helicopter 1000. Taken together, thedifferential angular motor speeds represent the change in angular speedof the motors 1008 required to achieve the desired position androtational orientation of the multi-rotor helicopter 1000 in theinertial frame of reference.

In some examples, the second controller 4020 maintains a vector of thecurrent state of the angular motor speeds and uses the vector of thecurrent state of the angular motor speeds to determine the difference inthe angular motor speeds required to achieve the desired position androtational orientation of the multi-rotor helicopter 1000 in theinertial frame of reference.

The vector of differential angular motor speeds, Δ

, is provided to the angular speed to voltage mapping function 4022which determines a vector of driving voltages:

$\overset{\_}{V} = \begin{bmatrix}V_{1} \\V_{2} \\\vdots \\V_{n}\end{bmatrix}$

As can be seen above, the vector of driving voltages,

, includes a driving voltage for each motor 1008 of the n thrusters1006. The driving voltages cause the motors 1008 to rotate at theangular speeds required to achieve the desired position and rotationalorientation of the multi-rotor helicopter 1000 in the inertial frame ofreference.

In some examples, the angular speed to voltage mapping function 4022maintains a vector of present driving voltages, the vector including thepresent driving voltage for each motor 1008. To determine the vector ofdriving voltages,

, the angular speed to voltage mapping function 4022 maps thedifferential angular speed, Δω_(i), for each motor 1008 to adifferential voltage. The differential voltage for each motor 1008 isapplied to the present driving voltage for the motor 1008, resulting inthe updated driving voltage for the motor, V_(i). The vector of drivingvoltages,

, includes the updated driving voltages for each motor 1008 of the ithrusters 1006.

The vector of driving voltages,

, is provided to the plant 4024 where the voltages are used to drive themotors 1008 of the i thrusters 1006, resulting in the multi-rotorhelicopter 1000 translating and rotating to a new estimate of positionand orientation:

$\left\lbrack \overset{¯}{\begin{matrix}X \\\overset{\_}{\Phi}\end{matrix}} \right\rbrack$

The observation module 4026 observes the new position and orientationand feeds it back to a combination node 4028 as an error signal. Thecontrol system 4000 repeats this process, achieving and maintaining themulti-rotor helicopter 1000 as close as possible to the desired positionand rotational orientation in the inertial frame of reference.

Referring to FIG. 28 , in an exemplary approach to controlling amulti-rotor helicopter relative to a mobile target, a multi-rotorhelicopter control system 4050 receives one or more sensor signals 4056from one or more sensors 4080. The one or more sensor signals 4056 areassociated with a position and a rotational orientation of the mobiletarget. The mobile target may be, for example, a mobile deliveryplatform connected to a car or a boat. The one or more sensor signals4056 are used by the control system 4050 to generate a vector ofvoltages,

, which are used to drive thrusters 1008 of the multi-rotor helicopter1000 to move the multi-rotor helicopter 1000 to the desired position inspace and the desired rotational orientation associated with theposition and the rotational orientation of the mobile target. Thisexemplary approach enables the multi-rotor helicopter 1000 toautomatically rotate the rotors to generate thrust to enable themulti-rotor helicopter 1000 to establish and maintain the position andthe rotational orientation of the mobile target. For example, themulti-rotor helicopter 1000 may establish and maintain the position andthe rotational orientation of the mobile target during deliveries to themobile target and/or during take-off and landing procedures associatedwith the mobile target.

The control system 4050 includes a first controller module 4068, asecond controller module 4070, an angular speed to voltage mappingfunction 4072, a plant 4074 (i.e., the multi-rotor helicopter 1000), anobservation module 4076, and a receiver module 4078. One or more sensorsignals 4056 from one or more sensors 4080 associated with the mobiletarget are wirelessly transmitted to the receiver module 4078. The oneor more sensor signals 4056 includes a position x (specified as, forexample, GPS coordinates) and a rotational orientation Φ_(x) (specified,for example, as a roll (R), pitch (P), and yaw (Y)) of the mobiletarget.

Receiver module 4078 transmits control signal 4066 to the firstcontroller 4068 based on the position and rotational orientation of themobile target received in the one or more sensor signals 4056. Controlsignal 4066 includes a desired position,

, in the frame of reference (specified as an n, w, h (i.e., North, West,height) coordinate system) and a desired rotational orientation

in the frame of reference (specified as a roll (R), pitch (P), and yaw(Y) in the frame of reference). As described below, control signal 4066is used to generate a vector of voltages,

, which are used to drive the thrusters 1008 of the multi-rotorhelicopter 1000 to move the multi-rotor helicopter 1000 to the desiredposition in space and the desired rotational orientation associated withthe mobile target. The frame of reference may be inertial ornon-inertial depending on the movement of the mobile target.

The control signal 4066, which is specified in the frame of reference isprovided to the first controller 4068 which processes the control signal4066 to determine a differential thrust force vector, Δ

, and a differential moment vector, Δ

, each specified in the frame of reference of the multi-rotor helicopter1000 (i.e., the x, y, z coordinate system) relative to the position ofthe mobile target. In some examples, differential vectors can be viewedas a scaling of a desired thrust vector. For example, the gain valuesfor the control system 4050 may be found using empiric tuning proceduresand therefore encapsulates a scaling factor. For this reason, in atleast some embodiments, the scaling factor does not need to beexplicitly determined by the control system 4050. In some examples, thedifferential vectors can be used to linearize the multi-rotor helicoptersystem around a localized operating point.

In some examples, the first controller 4068 maintains an estimate of thecurrent force vector and uses the estimate to determine the differentialforce vector in the frame of reference, Δ

, as a difference in the force vector required to achieve the desiredposition in the frame of reference. Similarly, the first controller 4068maintains an estimate of the current moment vector in the frame ofreference and uses the estimate to determine the differential momentvector in the frame of reference, ΔM, as a difference in the momentvector required to achieve the desired rotational orientation in theframe of reference. The first controller 4068 then applies a rotationmatrix to the differential force vector in the frame, ΔF, to determineits representation in the x, y, z coordinate system of the multi-rotorhelicopter 1000, Δ

. Similarly, the first controller 4068 applies the rotation matrix tothe differential moment vector in the frame of reference, ΔM, todetermine its representation in the x, y, z coordinate system of themulti-rotor helicopter 1000, Δ

.

The representation of the differential force vector in the x, y, zcoordinate system, Δ

, and the representation of the differential moment vector in the x, y,z coordinate system, Δ

, are provided to the second controller 4070 which determines a vectorof differential angular motor speeds:

${\Delta\overset{¯}{\omega}} = \begin{bmatrix}{\Delta\omega}_{1} \\{\Delta\omega}_{2} \\\vdots \\{\Delta\omega_{n}}\end{bmatrix}$

As can be seen above, the vector of differential angular motor speeds, Δ

, includes a single differential angular motor speed for each of the nthrusters 1006 of the multi-rotor helicopter 1000. Taken together, thedifferential angular motor speeds represent the change in angular speedof the motors 1008 required to achieve the desired position androtational orientation of the multi-rotor helicopter 1000 in the frameof reference relative to the mobile target.

In some examples, the second controller 4070 maintains a vector of thecurrent state of the angular motor speeds and uses the vector of thecurrent state of the angular motor speeds to determine the difference inthe angular motor speeds required to achieve the desired position androtational orientation of the multi-rotor helicopter 1000 in the frameof reference.

The vector of differential angular motor speeds, Δ

, is provided to the angular speed to voltage mapping function 4072which determines a vector of driving voltages:

$\overset{¯}{V} = \begin{bmatrix}V_{|} \\V_{2} \\\vdots \\V_{n}\end{bmatrix}$

As can be seen above, the vector of driving voltages,

, includes a driving voltage for each motor 1008 of the n thrusters1006. The driving voltages cause the motors 1008 to rotate at theangular speeds required to achieve the desired position and rotationalorientation of the multi-rotor helicopter 1000 in the frame ofreference.

In some examples, the angular speed to voltage mapping function 4072maintains a vector of present driving voltages, the vector including thepresent driving voltage for each motor 1008. To determine the vector ofdriving voltages,

, the angular speed to voltage mapping function 4072 maps thedifferential angular speed, Δω_(i), for each motor 1008 to adifferential voltage. The differential voltage for each motor 1008 isapplied to the present driving voltage for the motor 1008, resulting inthe updated driving voltage for the motor, V_(i). The vector of drivingvoltages,

, includes the updated driving voltages for each motor 1008 of the ithrusters 1006.

The vector of driving voltages,

, is provided to the plant 4074 where the voltages are used to drive themotors 1008 of the i thrusters 1006, resulting in the multi-rotorhelicopter 1000 translating and rotating to a new estimate of positionand rotational orientation:

$\left\lbrack \overset{¯}{\begin{matrix}X \\\overset{\_}{\Phi}\end{matrix}} \right\rbrack$

The observation module 4076 observes the new position and rotationalorientation and feeds it back to a combination node 4082 as an errorsignal. The new position and rotational orientation may be determinedusing an onboard camera(s) and/or onboard sensors and/or positioninginformation received from the one or more sensors 4080. The controlsystem 4050 repeats this process, achieving and maintaining themulti-rotor helicopter 1000 as close as possible to the desired positionand rotational orientation in the frame of reference relative to themobile target.

Referring to FIG. 29 , in some examples, a multi-rotor helicopter 1000is tasked to hover at a given position

in an inertial frame of reference in the presence a prevailing wind5030. For example, the multi-rotor helicopter 1000 may be performing apackage delivery requiring the multi-rotor helicopter 1000 to hoverabove a delivery location. The wind causes exertion of a horizontalforce,

, on the multi-rotor helicopter 1000, tending to displace themulti-rotor helicopter 1000 in the horizontal direction.

Conventional multi-rotor helicopters may have to tilt their frames intothe wind and adjust the thrust generated by their thrusters to counterthe horizontal force of the wind, thereby avoiding displacement.However, tilting the frame of a multi-rotor helicopter into windincreases the profile of the multi-rotor helicopter that is exposed tothe wind. The increased profile results in an increase in the horizontalforce applied to the multi-rotor helicopter due to the wind. Themulti-rotor helicopter must then further tilt into the wind and furtheradjust the thrust generated by its thrusters to counter the increasedwind force. Of course, further tilting into the wind further increasesthe profile of the multi-rotor helicopter that is exposed to the wind.It should be apparent to the reader that tilting a multi-rotorhelicopter into the wind results in a vicious cycle that wastes energy.

The approaches described above address this issue by enabling motion ofthe multi-rotor helicopter 1000 horizontally into the wind withouttilting the frame of the multi-rotor helicopter 1000 into the wind. Todo so, the control system described above causes the multi-rotorhelicopter 1000 to vector its net thrust such that a force vector

is applied to the multi-rotor helicopter 1000. The force vector

has a first component that extends upward along the h axis of theinertial frame with a magnitude equal to the gravitational constant, g,exerted on the multi-rotor helicopter 1000. The first component of theforce vector,

, maintains the altitude of the multi-rotor helicopter 1000 at thealtitude associated with the given position. The force vector,

, has a second component extending in a direction opposite (i.e., into)the force exerted by the wind and having a magnitude equal to themagnitude of the force,

, exerted by the wind. The second component of the force vectormaintains the position of the multi-rotor helicopter 1000 in the n, wplane of the inertial frame of reference.

To maintain its horizontal orientation, Φ, in the inertial frame ofreference, the control system described above causes the multi-rotorhelicopter 1000 to maintain the magnitude of its moment vector,

, at or around zero. In doing so, any rotation about the center of massof the multi-rotor helicopter 1000 is prevented as the multi-rotorhelicopter 1000 vectors its thrust to oppose the wind.

In this way the force vector,

, and the moment vector,

, maintained by the multi-rotor helicopter's control system enable themulti-rotor helicopter 1000 to compensate for wind forces appliedthereto without rotating and increasing the profile that the helicopter1000 presents to the wind.

Referring to FIG. 30 , it is often the case that an imaging sensor 6032(e.g., a camera) is attached to the multi-rotor helicopter 1000 for thepurpose of capturing images of a point of interest 634 on the groundbeneath the multi-rotor helicopter 1000. In general, it is oftendesirable to have the multi-rotor helicopter 1000 hover in one placewhile the imaging sensor 6032 captures images. Conventional multi-rotorhelicopters are unable to orient the imaging sensor 6032 without tiltingtheir frames (and causing horizontal movement) and therefore requireexpensive and heavy gimbals for orienting their imaging sensors.

The approaches described above obviate the need for such gimbals byallowing the multi-rotor helicopter 1000 to rotate its frame in theinertial plane while maintaining its position in the inertial plane. Inthis way, the imaging sensor 6032 can be statically attached to theframe of the multi-rotor helicopter 1000 and the helicopter can tilt itsframe to orient the imaging sensor 6032 without causing horizontalmovement of the helicopter. To do so, upon receiving a control signalcharacterizing a desired imaging sensor orientation,

, the control system described above causes the moment vector,

, of the multi-rotor helicopter 1000 to extend in a direction along thehorizontal (n, w) plane in the inertial frame of reference, with amagnitude corresponding to the desired amount of rotation. To maintainthe position,

, of the multi-rotor helicopter 1000 in the inertial frame of reference,the control system causes the multi-rotor helicopter 1000 to vector itsnet thrust such that a force vector,

, is applied to the multi-rotor helicopter 1000. The force vector,

, extends only along the h-axis of the inertial frame of reference andhas a magnitude equal to the gravitational constant, g. By independentlysetting the force vector,

, and the moment vector,

, the multi-rotor helicopter 1000 can rotate about its center whilehovering in one place.

As is noted above, conventional multi-rotor helicopters are controlledin roll, pitch, yaw, and net thrust. Such helicopters can becomeunstable (e.g., an oscillation in the orientation of the helicopter)when hovering in place. Some such helicopters include gimbaled imagingsensors. When a conventional helicopter hovers in place, its unstablebehavior can require that constant maintenance of the orientation ofgimbaled imaging sensor to compensate for the helicopter's instability.

Referring to FIG. 31 , the approaches described above advantageouslyreduce or eliminate the instability of a multi-rotor helicopter 1000when hovering by allowing for independent control of each axis of thehelicopter's orientation. In FIG. 31 , an imaging sensor 7032 isattached to the multi-rotor helicopter 1000 by a gimbal 7033. Theimaging sensor 7032 is configured to capture images on the groundbeneath the multi-rotor helicopter 1000. In general, it is oftendesirable to have the multi-rotor helicopter 1000 hover in one placewhile the imaging sensor 7032 is captures images of a given point ofinterest 7034.

To hover in one place with high stability, the multi-rotor helicopter1000 receives a control signal characterizing a desired spatialposition,

, and a desired spatial orientation,

, for the multi-rotor helicopter 1000. In the example of FIG. 31 , thedesired spatial orientation for the helicopter 1000 has the helicopterhovering horizontally with respect to the inertial frame of reference.

The control system described above receives the control signal andmaintains the spatial position,

, of the multi-rotor helicopter 1000 in the inertial frame of referenceby causing the multi-rotor helicopter 1000 to vector its net thrust suchthat a force vector,

, is applied to the multi-rotor helicopter 1000. The force vector,

, extends only along the h-axis of the inertial frame of reference andhas a magnitude equal to the gravitational constant, g.

The control system maintains the spatial orientation,

, of the multi-rotor helicopter 1000 by causing the multi-rotorhelicopter 1000 to vector its moment such that a moment vector,

, has a magnitude of approximately zero. The control system maintainsthe force vector,

, and the moment vector,

, such that the multi-rotor helicopter 1000 hovers in place with highstability.

Due to the high stability of the hovering multi-rotor helicopter 1000,little or no maintenance of the gimbal orientation is necessary to trainthe imaging sensor 7032 on the point of interest 7034.

In some examples, an imaging sensor 7032 and/or other sensor type (i.e.,a speed sensor, a position sensor, laser range finder, acoustic sensoretc.) may be attached to each spar of the multi-rotor helicopter 1000with a stationary mount or by a gimbal 7033.

In some examples, an aerodynamic body can be added to the multi-rotorhelicopter 1000 to reduce drag due to prevailing winds.

While the above approaches describe a helicopter including multiplethrusters, other types of thrust generators could be used instead of thethrusters.

While the above description relates mostly to the use of multi-rotorUAVs, other types of UAVs, such as those well known in the art can beused.

In some examples, the UAV (i.e., UAV 1102 and/or multi-rotor helicopter1000) includes deployable flaps that are deployed by the UAV to gainpositive lift. The deployable flaps may be added to the rotors of theUAV. For example, the flaps may be situated on the trailing edge of eachrotor to increase the lift. The UAV may retract the flaps for increasedstability while hovering.

In some examples, the UAV is programmed such that it always moves to alocation where there are not people present directly underneath the UAVbefore it lowers or drops the package.

While many of the UAV airframes described above include an even numberof rotors, in some examples, an odd number of rotors can be used (e.g.,in cases where one of the rotors is used for lateral movement of the UAVwhile the other rotors are used to provide vertical thrust).

It is to be understood that the foregoing description is intended toillustrate and not to limit the scope of the invention, which is definedby the scope of the appended claims. Other embodiments are within thescope of the following claims.

In some examples, a hybrid control scheme is used to control themulti-rotor helicopter. For example, the multi-rotor helicopter may usethe thrust vectoring approaches described above to maintain its positionin the presence of light winds but may switch to a classical tiltingstrategy if the prevailing wind becomes too strong to overcome with thethrust vectoring approaches.

It is noted that the control systems described above are only examplesof a control systems that can be used to control the multi-rotorhelicopter and other control systems using, for example, non-linearspecial Euclidean group 3 (i.e., SE(3)) techniques, can also be used.

In the examples described above, a multi-rotor helicopter includes sixthrust generators, each thrust generator generating thrust in adifferent direction from all of the other thrust generators. Bygenerating thrust in six different directions, all of the forces andmoments on the multi-rotor helicopter can be decoupled (i.e., the systemcan be expressed as a system of six equations with six unknowns). Insome examples, the multi-rotor helicopter can include additional (e.g.,ten) thrust generators, each generating thrust in a different directionfrom all of the other thrust generators. In such examples, the system isoverdetermined, allowing for finer control of at least some of theforces and moments on the multi-rotor helicopter. In other examples, themulti-rotor helicopter can include fewer than six thrust generators,each generating thrust in a different direction from all of the otherthrust generators.

In such examples, decoupling all of the forces and moments on themulti-rotor helicopter is not possible since the expression of such asystem would be underdetermined (i.e., there would be more unknowns thanthere would be equations). However, a system designer may select certainforces and/or moments to control independently, still yieldingperformance advantages in certain scenarios.

It should be understood that the configuration of the thrust locations,thrust directions, motor directions of rotation, and maximum rotationspeed or thrust produced by each motor can be selected according tovarious criteria, while maintaining the ability to control the multiple(e.g., six) motor speeds according to net linear thrust force (e.g.three constraints) and net torque (e.g., a further three constraints).In some examples, all the motors rotate in the same direction. For agiven set of thrust locations (e.g., a symmetric arrangement with thethrust locations at a fixed radius and spaced at 60 degrees), the thrustdirection are selected according to a design criterion. For example, thethrust directions are selected to provide equal thrust in a hover modewith the net force being vertical and no net torque. In some examples,the thrust directions are selected to achieve a desired controllability“envelope”, or optimize such an envelope subject to a criterion or a setof constraints, of achievable net thrust vectors given constraints onthe motor rotation speeds. As an example, the following set of thrustdirections provides equal torque and common rotation direction in ahover mode:

In one exemplary configuration, the twist angles are equal, but changingin sign. For example, the dihedral angle for each of the motors is +15degrees, and the twist angle for the motors alternates between +/−15degrees. For this exemplary configuration, the matrix

$\quad\begin{bmatrix}{- 2.50} & {- 0.72} & 6.79 & 0.63 & 1.18 & 0.18 \\2.50 & {- 0.72} & {- 6.79} & 0.63 & {- 1.18} & 0.18 \\1.87 & {- 1.81} & 6.79 & {- 1.33} & {- 0.05} & 0.18 \\{- 0.63} & 2.52 & {- 6.79} & 0.71 & 1.13 & 0.18 \\0.63 & 2.52 & 6.79 & 0.71 & {- 1.13} & 0.18 \\{- 1.87} & {- 1.81} & {- 6.79} & {- 1.33} & 0.05 & 0.18\end{bmatrix}$satisfies all of the above conditions.

If, however, the dihedral angle for the above configuration is −15, thenthe matrix

$\quad\begin{bmatrix}0.63 & {- 2.52} & 6.79 & 0.71 & 1.13 & 0.18 \\{- 0.63} & {- 2.52} & {- 6.79} & 0.71 & {- 1.13} & 0.18 \\1.87 & 1.81 & 6.79 & {- 1.33} & 0.05 & 0.18 \\2.50 & 0.72 & {- 6.79} & 0.63 & 1.18 & 0.18 \\{- 2.50} & 0.72 & 6.79 & 0.63 & {- 1.18} & 0.18 \\{- 1.87} & 1.81 & {- 6.79} & {- 1.33} & {- 0.05} & 0.18\end{bmatrix}$satisfies all of the above conditions.

In another exemplary configuration, the dihedral angle is +15, thepropellers all spin counter-clockwise, and the twist angle for themotors alternates between −22 and +8 degrees, then the matrix

$\quad\begin{bmatrix}1.18 & {- 1.92} & 3.69 & 0.78 & 1.16 & 0.18 \\{- 0.16} & {- 3.43} & {- 3.46} & 0.78 & {- 1.16} & 0.18 \\1.08 & 1.98 & 3.69 & {- 1.39} & 0.10 & 0.18 \\3.05 & 1.58 & {- 3.46} & 0.61 & 1.25 & 0.18 \\{- 2.25} & {- 0.06} & 3.69 & 0.61 & {- 1.25} & 0.18 \\{- 2.89} & 1.85 & {- 3.46} & {- 1.39} & {- 0.10} & 0.18\end{bmatrix}$satisfies all of the above conditions.

Referring to FIGS. 8-11 , a number of plots illustrate a controllabilityenvelope for an aerial vehicle configured with its motors spinning inalternating directions, a 15 degree dihedral angle, and alternating 15degree twist angle. In the configuration shown in the figures, the yawtorque on the vehicle is commanded to be 0 Nm and the propeller curvefor a 17×9″ propeller is used. Note that the propeller constant does notaffect generality.

Referring to FIG. 32 , a plot 8000 shows a roll and pitchcontrollability envelope in Nm at various vehicle weights, with nolateral thrust being generated.

Referring to FIG. 33 , a plot 9000 shows a roll and pitchcontrollability envelope in Nm at various vehicle weights with a 1 m/s²rightward thrust being generated.

Referring to FIG. 34 , a plot 9400 shows a roll and pitchcontrollability envelope in Nm at various vehicle weights with a 1 m/s²forward thrust being generated.

Referring to FIG. 35 , a plot 9600 shows a roll and pitchcontrollability envelope in Nm at various vehicle weights with a 1 m/s²forward thrust and 1 m/s² right thrust being generated.

FIG. 36 is a flowchart 3500 of an exemplary operation of a multi-rotorUAV converting between a multi-copter mode and a forward flight mode. Atoperation 3502, the rotors are in multi-copter mode. In multi-coptermode, the rotors are all in a substantially horizontal configuration(i.e., substantially parallel to the ground) allowing for verticaltake-off and landing, hovering, and low speed flight. In some examples,the at least some rotors tilt or rotate from a substantially verticalconfiguration into a substantially horizontal configuration.

At operation 3504, the UAV converts to forward flight mode when at leastsome of the rotors tilt or rotate such that they are in a substantiallyvertical configuration (i.e., substantially perpendicular to the ground)allowing for higher speed forward flight. For example, the liftingsurfaces on the spars connecting the at least some rotors to the centerof the fuselage rotate from a substantially horizontal configurationinto a substantially vertical configuration. Similarly, when the atleast some rotors tilt or rotate from a substantially horizontalconfiguration into a substantially vertical configuration, the liftingsurfaces on the spars rotate from a substantially vertical configurationto a substantially horizontal configuration.

In other examples, when the at least some rotors tilt or rotate betweena substantially vertical configuration and a substantially horizontalconfiguration, the lifting surfaces on the spars of the at least somerotors remain in a substantially horizontal configuration.

FIG. 37 is a flowchart 3600 of an exemplary multi-rotor UAV flying along distance in forward flight mode and a short distance inmulti-copter mode. In operation 3602, the UAV hovers or travel overshort distances and the rotors that are mounted in a substantiallyhorizontal position are used primarily, with the rotor mounted in asubstantially vertical position being used little, if at all.

In operation 3604, the UAV travels over longer distances with the rotormounted in a substantially vertical position relative to the groundacting as a propeller, moving the UAV in a lateral direction, with thestreamlined fuselage providing lift. The UAV may use the rotors mountedin a horizontal position to provide additional lift, if necessary.

In some examples, the spar that the horizontally mounted rotor ismounted upon is rotatable relative to the other spars of the UAV. Inoperation 3606, the spar may be rotated to alter the flightcharacteristics of the UAV and/or when the UAV switches between ahovering and a flying mode.

FIG. 38 is an electronics and control schematic block diagram for theUAV (i.e., UAV 1102 and/or multi-rotor helicopter 1000), according toone embodiment of the present disclosure. The UAV includes a system 70on a circuit board that integrates all Components of a computer or otherelectronic system using integrated circuits. In one embodiment, system70 manages the collection, scheduling, computation, transmission, andreceipt of data.

System 70 includes one or more non-transitory computer-readable mediafor storing one or more computer-executable instructions or software forimplementing exemplary embodiments. The non-transitory computer-readablemedia can include, but are not limited to, one or more types of hardwarememory, non-transitory tangible media (for example, one or more magneticstorage disks, one or more optical disks, one or more USB flashdrives),and the like. For example, a memory 28 included in system 70 can storecomputer-readable and computer-executable instructions or software forimplementing exemplary embodiments. System 70 also includes a processor30 and an associated core 31, and optionally, one or more additionalprocessor(s) 30′ and associated core(s) 31′ (for example, in the case ofcomputer systems having multiple processors/cores), for executingcomputer-readable and computer-executable instructions or softwarestored in memory 28 and other programs for controlling system hardware.Processor 30 and processor(s) 30′ can each be a single core processor ormultiple core (31 and 31′) processor. Memory 28 can include a computersystem memory or random access memory, such as DRAM, SRAM, EDO RAM, andthe like. Memory 28 can include other types of memory as well, orcombinations thereof.

System 70 can also include one or more storage devices, such as ahard-drive, CD-ROM, or other computer readable media, for storing dataand computer-readable instructions and/or software, that implementsembodiments of the control systems, as described herein, or portionsthereof. Exemplary storage device can also store one or more storagedevices for storing any suitable information required to implementexemplary embodiments and examples.

System 70 can include a data link 60 capable of secure transmission andreceipt of data placed on a tether or transmitted and receivedwirelessly. Data link 60 may be configured to transmit and receive datavia one or more network devices with one or more networks, for example,using a tethered connection or a wireless connections, or somecombination of the above. The data link 60 may include a built-innetwork adapter, network interface card, wireless network adapter, USBnetwork adapter, modem or any other device suitable for interfacing theUAV to any type of network capable of communication and performing theoperations described herein. In one embodiment, data link 60 is a seriallink, which may include a commercially available twisted pairtransceiver integrated circuit.

In some embodiments, a user can interact with the UAV through a visualdisplay device, such as a computer monitor. The visual display devicemay also display other aspects, elements and/or information or dataassociated with exemplary embodiments. The UAV may include other I/Odevices for receiving input from a user, for example, a keyboard and apointing device coupled to the visual display device. The UAV mayinclude other suitable conventional I/O peripherals.

System 70 can run an operating system 39, such as any of the versions ofthe Microsoft® Windows® operating systems, the different releases of theUnix and Linux operating systems, any version of the MacOS® forMacintosh computers, any embedded operating system, any real-timeoperating system, any open source operating system, any proprietaryoperating system, any operating systems for mobile computing devices, orany other operating system capable of running on the computing deviceand performing the operations described herein. In exemplaryembodiments, the operating system 39 can be run in native mode oremulated mode. In an exemplary embodiment, the operating system 39 canbe run on one or more cloud machine instances.

In one embodiment, one or more on-board data sensors may communicatewith the processor 30. For example, a gyroscope 44 may continuouslymeasure and integrate the angular rotation of the UAV. The gyroscope 44may comprise a micro-machined silicon integrated circuit available, forexample, from Analog Devices (ADI-16300 300 degrees per secondgyroscope). The processor 30 may continuously receive data from thegyroscope 44 and may compute and direct any correction to one or more ofthe electric motors 209. In an exemplary embodiment, the UAV includessix rotors 210 with each of the six rotors 210 is coupled to a motor 209to rotate the associated rotor 210. Motor 209 can include first andsecond motor elements, the first to control rotor speed, the second torotate the rotor assembly.

The processor 30 may also use data from the gyroscope 44 to correctangular drift by activating pitch servos 45, yaw servos 46, or acombination of both. The processor 30 may also control a tether servo 47to wind and unwind a tether from a spool. The processor 30 and othercontrol components may communicate via wireless signals when the tetheris disconnected. Accordingly, in one embodiment, the processor 30 and/orother control components or sensors described herein may comprisewireless controls or sensors, or a wireless data receiver or transceiverinterface.

In some cases, an accelerometer 43 continuously measures and integratesaccelerations in the three orthogonal physical planes of the UAV. In oneembodiment, the accelerometer 43 comprises an integrated circuitavailable from Analog Devices (ADI-16100 integrated 2 and 3 axisaccelerometer).

The UAV may also include an altimeter 41. The altimeter 41 allows theprocessor 30 to precisely hold altitude, or to ascend or descend in acontrolled manner. The altimeter 41 may facilitate, for example,traversing a stairwell or transitioning between floors of a building. Inone embodiment, the altimeter 41 is a digital pressure sensor.

Further, the UAV may have a global positioning system (GPS) module 42that can facilitate continuous monitoring of the position of the UAV.The processor 30 may act on the positional data provided by the GPSmodule 42 to allow the UAV to traverse particular paths. The GPS module42 may also report back an actual GPS position of the UAV to a groundstation. In one embodiment, the GPS module 42 is a miniature GPSreceiver.

In one embodiment, an optical imager digital signal processor (DSP)circuit 40 may utilize built-in optical computational features of anoptical mouse data pointing chip. Utilizing a suitable lens combinationpointing toward the earth's surface, the optical imager DSP circuit 40can update changes in physical position up to 6000 times per second. Forexample, the optical imager DSP 40 may be an Optical Mouse DigitalSignal Processing engine.

In one embodiment of the UAV including an observation device 12, theprocessor may communicate with the observation device 12 as well as apan servo 32, a tilt servo 34 operating servo motors, and a zoom servo35.

In certain configurations, the processor 30, the optical imager DSP 40,the altimeter 41, the GPS module 42, the accelerometer 43, and thegyroscope 44 can be fabricated as one or more integrated circuits thatreside on a printed circuit board assembly. The system can operate basedon wireless communications under battery power or can operate usingpower transmitted through a tether as described in U.S. Pat. No.9,290,269, the entire contents of which is incorporated herein byreference. The system can include flight stabilization and camerastabilization systems as described in U.S. Pat. Nos. 7,631,834 and8,736,676, the entire contents of these patents being incorporatedherein by reference. System 70 can include an inertial measurement unit(IMU) or be connected to a separate IMU circuit device.

The onboard processor can generate a change in flight path by alteringrotor speed, or altering rotor tilt angle, or a combination of both.Such command signals can be sent in response to on-board sensor dataindicating that a flight path change is needed to avoid a collision.Alternatively, the system can receive wireless commands from an externalflight controller that determines a collision avoidance path must beimplemented to avoid a collision with other objects such as buildings orother vehicles. Alternatively a remote pilot can assume control of thevehicle to avoid a collision. A parachute or automatic landinginstruction can also be used to land the vehicle.

System 70 transmits signals to one or more motors of the one or morerotors to adjust a configuration of the one or more rotors. In anexemplary embodiment, system 70 instructs the one or more motors toadjust the one or more of the rotors into a tilted, vertical orhorizontal configuration.

FIG. 39 is a block diagram of an UAV anti-collusion system, according toone embodiment of the present disclosure. The system includes one ormore drones (drone 80 and drone 81 shown), one or more control towers 84and one or more beacons 86. In the exemplary embodiment, drones 80, 81travel in a predetermined designated route. Each drone 80, 81 includes atransponder or another mechanism to detect and transmit signals tomonitor location. As the drones 80, 81 travel through a given airspacedivision 83, the drones 80, 81 are monitored by a first control towers84 responsible for that division. The first control tower 84 monitorsthe location and velocity of the drones 80, 81 and transmitsinstructions to the drones 80, 81. For example, the control tower 84communicates instructions to the drone 80 to avoid collisions withhazards, such as drone 81 and buildings 88 within the airspace division83. The control tower 84 may, for example, instruct the drone 80 toincrease its height to avoid the drone 81. As each drone 80, 81 leavesthat airspace division 83 and enters another, the first control tower 84passes it off to a second control tower 84 responsible for the newairspace division.

The one or more beacons 86 are further located along the predetermineddesignated route. The one or more beacons 86 transmit locationinformation to drones 80, 81. Drones 80, 81 may use the locationinformation to stay within the designated route and/or avoid hazards.

FIG. 40 is a multi-rotor helicopter 5000 includes a central body 5002from which a number (i.e., n) of rigid spars 5004 radially extend. Theend of each rigid spar 5004 includes two coaxial rotors 5006 rigidlymounted thereon. In the depicted embodiment, the rotors 5006 are in ahorizontal configuration. In some examples, each of the rotors 5006includes an electric motor 5008 (e.g., a brushless DC motor) whichdrives rotors 5006 to generate thrust. In some examples, the motor 5008may be used to tilt the associated rotor 5006. Generally, in operationthe central body 5002 includes a power source (for example, batteries5012) which provides power to the motors 5008 which in turn cause therotors 5006 to rotate. While rotating, each of the rotors 5006 forcesair above the helicopter 5000 in a generally downward direction togenerate a thrust having a magnitude and direction that can berepresented as a thrust vector (i.e., thrust vector 112). Multi-rotorhelicopter 5000 includes a plurality of sensors 5007 to detectsurroundings, a plurality of motors 5008 used to operate the rotors5006, a payload bay 5010, and one or more batteries 5012. Sensors 5007are located on each spar 5004 and may include, but not limited to,cameras and/or range finders, such as sonar or Lidar. Multi-rotorhelicopter 5000 includes stowed wings 5014 during a hover configuration.Each wing 5014 includes a motor 5015 to extend and retract the wing5014. Wings 5014 are extendable, as shown in FIG. 39 .

FIG. 40 is the multi-rotor helicopter 5000 as shown in FIG. 38 with thewings 5014 in an extended configuration. The wings 5014 extend to form acontinuous wing shape with a curve surface. The wings 5014 are locatedabove the rigid spar 5004. In the depicted embodiment, the rotors 5006are in a tilted and/or vertical configuration.

FIG. 42 is a multi-rotor helicopter 7000 includes a central body 7002from which a number (i.e., n) of rigid spars 7004 radially extend. Theend of each rigid spar 7004 includes a rotor 7006 rigidly mountedthereon. In the depicted embodiment, the rotors 7006 are in a horizontalconfiguration. In some examples, each of the rotors 7006 includes anelectric motor 7008 (e.g., a brushless DC motor) which drives rotors7006 to generate thrust. In some examples, the motor 7008 may be used totilt the associated rotor 7006. Generally, in operation the central body7002 includes a power source (or example, batteries 7012) which providespower to the motors 7008 which in turn cause the rotors 7006 to rotate.While rotating, each of the rotors 7006 forces air above the helicopter7000 in a generally downward direction to generate a thrust having amagnitude and direction that can be represented as a thrust vector(i.e., thrust vector 112). Multi-rotor helicopter 7000 includes aplurality of sensors 7007 to detect surroundings, a plurality of motors7008 used to operate the rotors 7006, a payload bay 7010, and one ormore batteries 7012. Multi-rotor helicopter 7000 includes stowed wings7014 during a hover configuration. Each wing 7014 includes a motor 7015to extend and retract the wing 7014. Wings 7014 are extendable, asdepicted in FIG. 39 . The wing surface area can be adjusted incombination with tilt angle and rotor speed to provide the required liftto the vehicle. Note that the spars 7004 can be rotated 7016 verticallyand/or horizontally in certain embodiments to improve stability.

FIG. 43 is a block diagram of a rotor assembly 6000 using adaptivethrust vectoring to change rotor positioning in a UAV (i.e., UAV 1102and/or multi-rotor helicopter 1000), according to one embodiment of thepresent disclosure. In an exemplary embodiment, two motor mount servos6002 are mounted to a motor mount 6004. The motor mount 6004 coupled toa spar 6006. The motor mount servos 6002 are also coupled to a placementplate 6008. The placement plate 6008 is movable on a horizontal plane bythe motor mount servos 6002. Movement of the placement plate 6008 causesmotion in a first linkage 6009 coupled to a first ball joint 6010.Movement in the first ball joint 6010 causes motion in a second linkage6011. The second linkage 6011 is coupled to a second ball joint 6012.Movement of the second linkage 6011 causes motion in the second balljoint 6012, which in turn causes motion in a third linkage 6013. Thethird linkage 6013 is coupled to an axis platform 6014 coupled to arotor 6016. The movement of the third linkage 6013 in turn tilts theaxis platform 6014 and the rotor 6016.

The ball joints 6010, 6012 permit movement of linkages 6009, 6011, and6013. The tilting of the axis platform 6014 is dependent on the degreeof movement of the placement plate 6008 controlled by the motor mountservos 6002. An axis 6020 runs through the center of linkages 6009,6011, and 6013. In one embodiment, the axis 6020 is a metal rod.

The motor mount servos 6002 are used for fine tuning and control of thetilting of rotor 6016. The motor mount servos 6002 controls the tiltingand/or pitch of the rotor 6016 by the linkage, which tilts the rotor6016 in varies degrees of freedom.

In some embodiments, the spar 6006 is coupled to a motor 6025 configuredto rotate the rotor assembly 6000.

Referring to FIG. 44 is a flowchart 4300 of an exemplary multi-rotor UAV(i.e., UAV 1102 and/or multi-rotor helicopter 1000) configured to tiltone or more rotors while traveling a route. In an exemplary embodiment,the route may include different velocities required at differentportions of the route and/or different atmospheric conditions atdifferent portions of the route. For example, a portion of the route mayrequire a traveling speed of a UAV limited to 35 miles per hour.

At operation 4302, a control system (i.e., system 70) of the UAV isprogrammed with preset configurations for traveling the route. In apreferred embodiment, the twist angle can be adjusted before or duringflight based on one or more factors. The programmed velocity or thecontrol systems' response to received instructions to increase velocitycan be implemented by an increase in rotor speed of one or more rotors,by increasing the tilt angle of one or more rotors, or a combination ofboth. For example, by increasing the tilt angle, the lateral and/orrotational velocity of the vehicle can be increased. If all the rotors(e.g. four, six or eight rotors) are all tilted to an increased anglebetween 25 and 35 degrees, for example, there is a decrease in verticallift capacity but an increase in the lateral velocity that the vehiclecan achieve at a given rotor speed. If the aerial vehicle has limitedlift surface area, it can be desirable to retain a fraction of liftcapacity for a given desired lateral velocity. As there can be differentvelocities required at different portions of the route, or the directionof the wind can change at different portions of the route that require achange in the twist angle to maintain velocity, there can be selectedpresets on the tilt angle that are programmed into the system. Forexample, the UAV may have twist angles of +/−25 degrees at launch, thenrotate the twist angles to +/−35 degrees to increase lateral velocity toa certain level after a specified altitude and position are reached. Thevehicle can then navigate to another point along its flight path whereit can further increase flight speed and consequently shift the twistangle a second time to +/−40 degrees. The vehicle can then reduce thetwist angle to +/−25 degrees as it approaches a landing or hoveringlocation. Note that the dihedral angle can also be adjusted dynamicallyas well with the use of motors within the aerial vehicle body that canmove the spars both vertically and laterally. The preset tilt angle canhave ranges, such as 30-40 degrees, 40-50 degrees, or 50-60 degrees asrequired for the specific application and flight conditions. This systemcan be used to adjust the tilt angle of each rotor independently overthe range of 0-90 degrees to obtain a selected flight path. Thisprocedure can be used for additional applications in addition to packagedelivery, such as surveillance, launching or landing on a movingvehicle, target tracking, and in both tethered and non-tethered modes ofoperation.

At operation 4304, the control system receives a velocity of the UAV anda GPS coordinate to determine a current location on the route. Atoperation 4306, the control system adjusts the tilt angle of one or morerotors based on the GPS coordinate and/or the velocity and/oratmospheric conditions. For example, based on the GPS coordinate, thecontrol system may determine that the UAV is located within an area ofthe route where the velocity is limited to predefined parameters. Thecontrol system then adjusts the tilt angle of one or more rotors todecrease or increase the velocity of the UAV to within the predefinedparameters

The one or more rotors can be tilted at different angles in order tocontrol the direction and the velocity of the UAV. The control systemmay control the direction and the velocity of the UAV using fine motorcontrol or gross motor control. Gross motor control includes rotatingone or more spars using a motor. Fine motor control includes tilting theone or more rotors using, for example, motor mount servos.

An advantage of this control system is the ability to adjust todifferent weight distributions for articles that are loaded onto thevehicle for transport. For the delivery of articles purchased bycustomers using the process depicted in FIG. 1 , for example, it may notbe possible to mount an item or package into the payload withoutaltering the center of gravity of the vehicle. The flight control systemcan automatically account for this change in weight distribution byadjusting rotor speed, twist angle, dihedral angle of one or more sparsor the lateral orientation of one or more spars relative to the aerialbody, or by adjusting flight control surfaces such as flaps or wings.

Referring to FIG. 45 , in an exemplary approach to controlling a vehicle100, a multi-rotor helicopter control system 4400 receives a controlsignal 4416 including a desired position,

, in the inertial frame of reference (specified as an n, w, h (i.e.,North, West, height) coordinate system (where the terms “inertial frameof reference” and n, w, h coordinate system are used interchangeably),and a desired rotational orientation,

, in the inertial frame of reference (specified as a roll (R), pitch(P), and yaw (Y) in the inertial frame of reference), and generates avector of voltages

which are used to drive the thrusters 1008 of the multi-rotor helicopter1000 to move the multi-rotor helicopter 1000 to the desired position inspace and the desired rotational orientation.

The control system 4400 includes a first controller module 4418, asecond controller module 4420, an angular speed to voltage mappingfunction 4422, a plant 4424 (i.e., the multi-rotor helicopter 1000), andan observation module 4426. The control signal 4416, which is specifiedin the inertial frame of reference is provided to the first controller4418 which processes the control signal 4416 to determine a differentialthrust force vector, Δ

and a differential moment vector, Δ

, each specified in the frame of reference of the multi-rotor helicopter1000 (i.e., the x, y, z coordinate system). In some examples,differential vectors can be viewed as a scaling of a desired thrustvector. For example, the gain values for the control system 4400 may befound using empiric tuning procedures and therefore encapsulates ascaling factor. For this reason, in at least some embodiments, thescaling factor does not need to be explicitly determined by the controlsystem 4400. In some examples, the differential vectors can be used tolinearize the multi-rotor helicopter system around a localized operatingpoint.

In some examples, the first controller 4418 maintains an estimate of thecurrent force vector and uses the estimate to determine the differentialforce vector in the inertial frame of reference, Δ

, as a difference in the force vector required to achieve the desiredposition in the inertial frame of reference. Similarly, the firstcontroller 4418 maintains an estimate of the current moment vector inthe inertial frame of reference and uses the estimate to determine thedifferential moment vector in the inertial frame of reference, Δ

, as a difference in the moment vector required to achieve the desiredrotational orientation in the inertial frame of reference. The firstcontroller 4418 then applies a rotation matrix to the differential forcevector in the inertial frame, Δ

, to determine its representation in the x, y, z coordinate system ofthe multi-rotor helicopter 1000, Δ

. Similarly, the first controller 4418 applies the rotation matrix tothe differential moment vector in the inertial frame of reference, Δ

, to determine its representation in the x, y, z coordinate system ofthe multi-rotor helicopter 1000, Δ

.

The representation of the differential force vector in the x, y, zcoordinate system, Δ

, and the representation of the differential moment vector in the x, y,z coordinate system, Δ

, are provided to the second controller 4420 which determines a vectorof differential angular motor speeds:

${\Delta\overset{¯}{\omega}} = \begin{bmatrix}{\Delta\omega}_{1} \\{\Delta\omega}_{2} \\\vdots \\{\Delta\omega}_{n}\end{bmatrix}$

As can be seen above, the vector of differential angular motor speeds, Δ

, includes a single differential angular motor speed for each of the nthrusters 1006 of the multi-rotor helicopter 1000. Taken together, thedifferential angular Motor speeds represent the change in angular speedof the motors 1008 required to achieve the desired position androtational orientation of the multi-rotor helicopter 1000 in theinertial frame of reference.

In some examples, the second controller 4420 maintains a vector of thecurrent state of the angular motor speeds and uses the vector of thecurrent state of the angular motor speeds to determine the difference inthe angular motor speeds required to achieve the desired position androtational orientation of the multi-rotor helicopter 1000 in theinertial frame of reference.

The vector of differential angular motor speeds, Δ

, is provided to the angular speed to voltage mapping function 4422which determines a vector of driving voltages:

$\overset{¯}{V} = \begin{bmatrix}V_{1} \\V_{2} \\\vdots \\V_{n}\end{bmatrix}$

As can be seen above, the vector of driving voltages,

, includes a driving voltage for each motor 1008 of the n thrusters1006. The driving voltages cause the motors 1008 to rotate at theangular speeds required to achieve the desired position and rotationalorientation of the multi-rotor helicopter 1000 in the inertial frame ofreference.

In some examples, the angular speed to voltage mapping function 4422maintains a vector of present driving voltages, the vector including thepresent driving voltage for each motor 1008. To determine the vector ofdriving voltages,

, the angular speed to voltage mapping function 4422 maps thedifferential angular speed Δω_(i) for each motor 1008 to a differentialvoltage. The differential voltage for each motor 1008 is applied to thepresent driving voltage for the motor 1008, resulting in the updateddriving voltage for the motor, V_(i). The vector of driving voltages,

, includes the updated driving voltages for each motor 1008 of the ithrusters 1006.

The vector of driving voltages,

, is provided to the plant 4424 where the voltages are used to drive themotors 1008 of the i thrusters 1006, resulting in the multi-rotorhelicopter 1000 translating and rotating to a new estimate of positionand orientation:

$\left\lbrack \overset{¯}{\begin{matrix}X \\\overset{\_}{\Phi}\end{matrix}} \right\rbrack$

At least one sensor 4426 includes one or more of an inertial measurementunit (IMU) sensor, gyroscope and accelerometer sensors, a GPS sensor, aLidar sensor, or a radar sensor, as further described in FIG. 46 . Thesensor 4426 obtains data and feeds it back to a combination node 4428 asan error signal. The control system 4400 repeats this process, achievingand maintaining the multi-rotor helicopter 1000 as close as possible tothe desired position and rotational orientation in the inertial frame ofreference.

FIG. 46 is an schematic block diagram of the at least one sensor 4426shown in FIG. 45 used in the multi-rotor helicopter control system 4400for controlling a vehicle 100. Sensor 4426 includes one or more of aradar sensor 4502, an inertial measurement unit (IMU) sensor 4504, a GPSsensor 4506, a Lidar sensor 4508, a pressure sensor 4510, a gyroscopesensor 4512, and an accelerometer sensor 4514.

The data collected from the IMU sensor 4504 enables the control system4400 to track the UAV's position, i.e., using, for example, deadreckoning, or to adjust for wind.

The pressure sensor 4510 measures atmospheric pressure. Data provided bythe pressure sensor 4510 enabling the control system 4400 to adjustother parameters (i.e., rotor speed, tilting angle, etc.) based on theatmospheric pressure.

The radar sensor 4502 provide detection of objects, reliable distancemeasurement, collision avoidance, and driver assistance. Data providedby the radar sensor 4502 is used by the control system 4400 to computeupdated rotor speed to avoid collisions.

The GPS sensor 4506 provides accurate position and velocity information.Data provided by the GPS sensor 4506 is used by the control system 4400to compute updated location and velocity information.

The Lidar sensor 4508, which measures distance to a target byilluminating that target with a laser light, provide detection ofobjects, reliable distance measurement, collision avoidance and driverassistance. Data provided by the Lidar sensor 4502 is used by thecontrol system 4400 to compute updated rotor speed to avoid collisions.

The gyroscope sensor 4512 measures the angular rotational velocity, andassists with orientation and stability in navigation. The accelerometersensor 4514 measures linear acceleration of movement. Data provided bythe gyroscope sensor 4512 and accelerometer sensor 4514 is used by thecontrol system 4400 to compute updated linear and rotation velocity.

FIG. 47 is a flowchart 4600 of an exemplary multi-rotor UAV configuredto deliver items to a mobile delivery location, such as directly to acustomer at the location of their mobile device. At operation 4602, aflight path is entered into a UAV, including geographic deliverylocation data. At operation 4604, the UAV updates the geographicdelivery location data whenever the delivery location has moved, such asby receiving updated data from a mobile device.

In some embodiments, at operation 4606, the UAV uses a camera to verifythe moved delivery location. At operation 4608, the UAV uses the updateddelivery location data to deliver an item.

What is claimed is:
 1. An unmanned aerial vehicle operable in a firstmode and a second mode, and comprising: a fuselage; one or more tiltablerotors each of which is tiltable between the first mode and the secondmode in which the tiltable rotor is closer to vertical configuration andfarther from horizontal configuration than in the first mode; one ormore spars each of which is coupled to the fuselage and to a respectivetiltable rotor, with a rotatable lifting surface on each spar, therotatable lifting surface being rotatable between the first mode and thesecond mode in which the rotatable lifting surface is closer tohorizontal configuration and farther from vertical configuration than inthe first mode.
 2. The unmanned aerial vehicle of claim 1, wherein thefirst mode is for use in vertical take-off and/or landing and/orhovering.
 3. The unmanned aerial vehicle of claim 1, wherein the secondmode is for use in a flight in a lateral direction.
 4. The unmannedaerial vehicle of claim 3, wherein at least one rotatable liftingsurface provides a lift in the flight in the lateral direction.
 5. Theunmanned aerial vehicle of claim 1, wherein in the first mode, eachtiltable rotor is in substantially horizontal configuration suitable forvertical take-off and/or landing and/or hovering and/or a flight in alateral direction at speeds lower than in the second mode, and eachrotatable lifting surface is in substantially vertical configuration. 6.The unmanned aerial vehicle of claim 1, wherein in the second mode, eachtiltable rotor is in substantially vertical configuration suitable for aflight in a lateral direction, and each rotatable lifting surface is insubstantially horizontal configuration with at least one rotatablelifting surface providing a lift in the flight in the lateral direction.7. The unmanned aerial vehicle of claim 1, wherein: in the first mode,each tiltable rotor is in substantially horizontal configurationsuitable for vertical take-off and/or landing and/or hovering and/or aflight in a lateral direction at speeds lower than in the second mode,and each rotatable lifting surface is in substantially verticalconfiguration; and in the second mode, each tiltable rotor is insubstantially vertical configuration suitable for the flight in thelateral direction, and each rotatable lifting surface is insubstantially horizontal configuration.
 8. The unmanned aerial vehicleof claim 7, wherein at least one rotatable lifting surface provides alift in the second mode.
 9. The unmanned aerial vehicle of claim 1,wherein the one or more tiltable rotors are a plurality of tiltablerotors.
 10. The unmanned aerial vehicle of claim 1, further comprising:one or more additional tiltable rotors each of which is tiltable betweenthe first mode and the second mode in which the additional rotor iscloser to vertical configuration and farther from horizontalconfiguration than in the first mode; one or more spars each of which iscoupled to the fuselage and to a respective one of the additionaltiltable rotors, with a non-rotatable lifting surface on each spar. 11.The unmanned aerial vehicle of claim 1, wherein the fuselage is shapedto provide an airplane-type lift in a flight in a lateral direction. 12.A method for operating the unmanned aerial vehicle of claim 1, themethod comprising controlling the unmanned aerial vehicle to: perform avertical take-off and/or landing and/or hovering by using the one ormore tiltable rotors positioned for the first mode, with thecorresponding lifting surfaces positioned for the first mode; tilt theone or more tiltable rotors into position for the second mode, androtate the corresponding one or more rotatable lifting surfaces intoposition for the second mode, for a flight in a lateral direction, atleast one rotatable lifting surface providing a lift during the flightin the lateral direction.
 13. A method for operating an unmanned aerialvehicle comprising a fuselage, the method comprising: tilting each ofone or more tiltable rotors of the unmanned aerial vehicle between afirst position of the tiltable rotor and a second position of thetiltable rotor, wherein the second position is closer to vertical andfarther from horizontal than the first position; and rotating arotatable lifting surface on each of one or more spars coupled to thefuselage, the rotatable lifting surface connecting a respective tiltablerotor to a fuselage of the vehicle, the rotatable lifting surface beingrotated between a first position of the rotatable lifting surface and asecond position of the rotatable lifting surface, wherein the secondposition is closer to horizontal and farther from vertical than thefirst position.
 14. The method of claim 13, further comprisingcontrolling the vehicle to take off and fly in a lateral direction,wherein each tiltable rotor and rotatable lifting surface are closer totheir respective first positions during take-off than during at leastpart of a flight in the lateral direction.
 15. The method of claim 14,further comprising landing the vehicle with each tiltable rotor and eachrotatable lifting surface being closer to their respective firstpositions than during at least part of the flight in the lateraldirection.
 16. The method of claim 14, further comprising controllingthe vehicle to hover with each tiltable rotor and each rotatable liftingsurface being closer to their respective first positions than during atleast part of the flight in the lateral direction.
 17. The method ofclaim 14, wherein at least one rotatable lifting surface provides a liftduring at least part of the flight in the lateral direction.
 18. Themethod of claim 14, wherein the taking off is vertical.
 19. The methodof claim 14, wherein the flight in the lateral direction comprises afirst flight portion and a second flight portion at speeds higher thanin the first flight portion, and each tiltable rotor and rotatablelifting surface are closer to their respective second positions duringthe second flight portion than during the first flight portion.
 20. Themethod of claim 13, wherein the one or more tiltable rotors are aplurality of rotors.